Pt-induced semimetallic transport and enhanced thermoelectric response in the half-Heusler alloy YNi 0.5Pt 0.5Bi

arXiv:2610.22253 · cond-mat.str-el, cond-mat.mtrl-sci · Submitted 2026-10-15 · Read on arXiv

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Introduction to the show: ident: Quantum Radio. Generated commentary on the latest quantum physics and condensed matter papers.

Kai: I'm Kai.

Mira: And I'm Mira, here with Lev.

Kai: Today's paper: "Pt-induced semimetallic transport and enhanced thermoelectric response in the half-Heusler alloy YNi 0.5Pt 0.5Bi".

Mira: The gist: Pt alloying transforms transport behavior towards a semimetallic state with holedominated conduction, a low hole carrier concentration of (1.9 × 1019 cm−3),

Kai: First, who's behind it and why it matters.

Title and authors: Kai: Moving on, let's talk about this paper's title again: "Pt-induced semimetallic transport and enhanced thermoelectric response in the half-Heusler alloy YNi 0 point 5Pt 0 point 5Bi". It really tells you exactly what the authors are trying to achieve with this specific material system.

Mira: Yeah, that title is pretty descriptive because it highlights two main outcomes: the semimetallic transport and the enhanced thermoelectric response, which they achieved through Pt alloying.

Lev: What I mean is, they're not just tweaking things randomly; they’re specifically aiming to use Pt as a tool to achieve those two distinct improvements in this half-Heusler alloy.

Kai: Right. So it’s not just about adding an element; it’s about using the specific alloying of Ni and Pt to get these two different benefits in terms of transport and thermoelectric metrics.

Mira: Exactly. And the authors emphasize that they are looking at how this substitution or doping can be applied to enhance or tune properties, which is a common theme in materials research.

Lev: It confirms that tuning properties via alloying isn't just a general technique; it's a targeted approach when you have specific targets like semimetallic behavior and better thermoelectric performance.

Kai: So it frames the study as an effort to find the right balance where you can simultaneously get these desired transport changes and those better power factor results.

Mira: And they set up the experiment to test that exact hypothesis by synthesizing YNi0 point 5Pt0 point 5Bi pellets using spark-plasma-sintering at a pressure of seventy megapascal and a temperature of six hundred fifty degrees celsius.

Lev: From an engineering standpoint, that SPS method is pretty standard for making dense pellets, so we know the synthesis process itself is relatively straightforward to replicate in a lab setting.

Kai: But the actual characterization—the electrical resistivity, Hall resistivity, and magnetotransport—that’s where it gets interesting because those are the properties they are directly measuring.

Mira: And their structural characterization using powder X-ray diffraction confirmed that the compound is single phase with a lattice parameter of six point five hundred forty-one angstroms.

Lev: A single phase result is crucial for any reliable measurement, so if it wasn't single phase, all those transport measurements would be meaningless.

Kai: So to summarize this segment, they are using the specific combination of Ni and Pt in YNi0 point 5Pt0 point 5Bi to aim for a semimetallic transport state and enhanced thermoelectric response through careful synthesis and characterization steps involving spark-plasma-sintering and X-ray diffraction <ref:2610.22253#pg1>.

Mira: And the title sets the stage perfectly by telling us exactly what kind of material transformation they are investigating by focusing on these two key physical outcomes.

Lev: It’s a focused study on using alloying to achieve specific, measurable improvements in both transport behavior and thermoelectric figures of merit.

The paper's summary: Kai: Now, let's look at the actual summary of "Pt-induced semimetallic transport and enhanced thermoelectric response in the half-Heusler alloy YNi 0 point 5Pt 0 point 5Bi". They detail how they synthesized the material and characterized it using a bunch of techniques.

Mira: They describe arc melting high purity elements to form YNi0 point 5Pt0 point 5 ingots, which were then crushed and mixed with Bi pieces before subjecting them to spark-plasma-sintering at seventy megapascals and six hundred fifty degrees celsius to get the final pellets.

Lev: So they’re describing a fairly standard materials synthesis route here, but we know SPS is good for getting good density in these types of compounds, so that part is solid engineering practice.

Kai: They used energy-dispersive X-ray spectroscopy to determine the elemental composition, showing nearly one third composition of Y and Bi elements with approximately equal shares of Ni and Pt in the mix.

Mira: Structurally, powder X-ray diffraction confirmed it's a single phase compound with a lattice parameter of six point five hundred forty-one angstroms.

Lev: That structural confirmation is vital for the measurements, so if they had some secondary phases, those would have messed up the electrical data significantly.

Kai: They also used DFT calculations to confirm that Pt-induced closing of the electronic band gap and a low density of states near the Fermi level, consistent with semimetal-like transport.

Mira: The DFT results suggest that this material behaves like a semimetal because the Fermi level crosses both the valence band and conduction band at Gamma and X high symmetry locations, with higher Pt orbital projection in both VBM and CBM at Gamma and CBM at X > page two of that work reads: "ARPES studies of YPtBi confirm the presence of a Dirac cone at the Γ point, located five hundred meV below the Fermi energy2" <ref:2610.22253#pg2,ARPES studies of YPtBi confirm the presence of a Dirac cone at>.

Lev: That finding about the Dirac cone is really important because it connects this DFT picture to what we might expect from solid-state physics.

Kai: They also found that their electrical resistivity shows temperature dependence similar to YPtBi but deviates from its perfectly linear behavior at low temperatures, which hints at some more complex physics happening there.

Mira: The Arrhenius equation, rho equal rho zero exp Eg squared k BT, was used to calculate the energy band gap, Eg, which they found to be zero point forty-nine electron volt.

Lev: So they are using that Arrhenius fit on the high-temperature resistivity slope between ln rho versus one over T to extract this apparent activation energy of zero point forty-nine electron volt.

Kai: That apparent activation energy is what they use to estimate the band gap, and it’s a bit lower than what you might expect for a standard semiconductor.

Mira: The Arrhenius fit also shows that the temperature dependent behavior of resistivity for YNi0 point 5Pt0 point 5Bi is similar to the temperature dependent behavior of resistivity for YPtBi > page three of that work reads: "The temperature dependent behavior of resistivity for YNi0 point 5Pt0 point 5Bi is similar to temperature dependent behavior of resistivity for YPtBi" <ref:2610.22253#pg1>.

Lev: So they are establishing a comparison point with a known material, which is good grounding when you're trying to interpret their results.

Kai: They also found that the Hall resistivity dependence showed a positive value for the Hall coefficient, which indicates hole dominant transport in YNi0 point 5Pt0 point 5Bi <ref:2610.22253#pg1>.

Mira: And they found that the hole charge carrier density at three hundred Kelvin was one point nine times ten to the power of nineteen centimeters cubed, and the hole charge carrier mobility at three hundred Kelvin was found to be equal to two hundred fifty-five point eight centimeters squared per volt per second.

Lev: That mobility number is what we need to see on real hardware; a higher value means better performance in terms of carrier transport efficiency.

Kai: So the summary boils down to them synthesizing the material, characterizing it with XRD, DFT, and electrical measurements showing a low hole carrier concentration of one point nine times ten to the power of nineteen centimeters cubed and a mobility of two hundred fifty-five point eight centimeters squared per volt per second.

Mira: And they are also highlighting the key finding that Pt alloying closes the electronic band gap and leads to semimetal-like transport, which is consistent with their other results.

Lev: It’s a summary of how they confirmed their initial hypothesis using multiple experimental and theoretical tools to build a robust picture of this new material system.

The paper's improvements: Kai: Okay, so we've seen the results—low carrier concentration, mobility, and the thermoelectric figures of merit. Now let’s talk about what the paper suggests are the actual improvements they found by using Pt alloying.

Mira: They point out that they have an improved Seebeck coefficient of one hundred thirty microvolt per kelvin cubed compared to about ninety microvolt per kelvin cubed for YNiBi.

Lev: That jump in the Seebeck coefficient is significant because it shows that the material has a better ability to generate voltage from its charge carriers under these conditions.

Kai: And they also found that the power factor attained a maximum value of thirteen point seven microwatt centimeter per kelvin squared at three hundred Kelvin, which is marginally higher than about eleven point four microwatt centimeter per kelvin squared for YNiBi.

Mira: So these are the direct metrics they are using to prove that Pt alloying actually enhances the material's thermoelectric performance compared to the baseline YNiBi.

Lev: These figures, especially the figure of merit zT equal to zero point thirteen at three hundred Kelvin, which is a clear improvement over pristine YNiBi.

Kai: And they are also suggesting that this trend of zT increasing at three hundred Kelvin suggests that YNi0 point 5Pt0 point 5Bi has the potential to exhibit even better thermoelectric performance at higher temperatures down the road <ref:2610.22253#pg3>.

Mira: They're also pointing out that alloy-disorder-induced phonon scattering reduces the thermal conductivity, which is good because it means they can engineer materials with lower lattice thermal conductivity compared to baseline compounds like YNiBi.

Lev: That reduced thermal conductivity is something we need to account for in our models because it means the material isn't just a perfect conductor of heat; there’s complexity introduced by the mixing.

Kai: So basically, they are showing that this alloy-disorder effect helps them get better performance metrics across the board compared to their baseline, YNiBi.

Mira: And they also have these AI systems that can predict optimal alloying compositions for half-Heusler alloys by utilizing "Pt alloying increases the room-temperature Seebeck coefficient from approximately ninety to one hundred thirty microvolt per kelvin cubed" and "the tuning of lattice parameter by mixing Ni and Pt will optimise the hybridization strength to bring the conditions for desired band inversion."

Lev: That points toward a real design path where we can use computational tools to guide us toward those specific compositional targets mentioned in their findings.

Kai: And they also have an AI system that performs materials screening based on predicted thermoelectric performance by calculating the figure of merit zT equal to zero point thirteen for candidate compounds, allowing prioritization of alloys with enhanced performance over pristine YNiBi.

Mira: That’s a powerful combination, moving from just reporting results to creating tools that help predict what we should try next.

Lev: It shows the value in integrating theoretical predictions and experimental measurements into an AI framework to streamline the discovery process for new thermoelectric materials.

Conclusion: Kai: So wrapping up this discussion on "Pt-induced semimetallic transport and enhanced thermoelectric response in the half-Heusler alloy YNi 0 point 5Pt 0 point 5Bi", the core message is that Pt alloying transforms the material towards a semimetallic state with holedominated conduction, a low hole carrier concentration of one point nine times ten to the power of nineteen centimeters cubed, and a sizeable non-saturating magnetoresistance of eighteen percent at three hundred Kelvin under fourteen Tesla.

Mira: They've shown that this leads to an improved Seebeck coefficient of one hundred thirty microvolt per kelvin cubed, and the power factor reaches thirteen point seven microwatt centimeter per kelvin squared at three hundred Kelvin, and the figure of merit zT reaches zero point thirteen.

Lev: And they also highlighted that alloy-disorder-induced phonon scattering reduces thermal conductivity, which is good because it means they can engineer materials with lower lattice thermal conductivity compared to baseline compounds like YNiBi.

Kai: So what this means for us is that we have a material where we can design it to have better thermoelectric performance by using alloying strategies guided by these theoretical insights and experimental measurements.

Lev: For future work, it seems like the focus will be on pushing this further toward higher temperatures and understanding how those disorder effects evolve as we move away from room temperature conditions.

Vikas Chahar, Shivam Rathod, Lankun Wang, Sneh, Shubhadeep Bej, Divya Prakash Dubey, Dinesh Dixit, Abdelmoneim Elkhouly, Raúl Cardoso-Gil, Zihang Liu, Xiao Xu, Rie Y. Umetsu, Ratnamala Chatterjee

Department of Physics, Indian Institute of Technology Delhi · State Key Laboratory of Precision Welding and Joining of Materials and Structures, Harbin Institute of Technology · Department of Microtechnology and Nanoscience, Chalmers University of Technology · Central Research Facility, Indian Institute of Technology Delhi · Physics Department, Faculty of Science, Damanhour University · Max-Planck-Institut für Chemische Physik fester Stoffe · Department of Materials Science, Graduate School of Engineering, Tohoku University

cond-mat.str-el, cond-mat.mtrl-sci

Submitted: 2026-10-15

Updated: 2026-10-15

Comments: 10 pages, 5 figures, 2 tables

License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/

Importance score: 83/100

The gist: The gist: Pt alloying transforms transport behavior towards a semimetallic state with holedominated conduction, a low hole carrier concentration of (1.9 × 1019 cm−3), and a sizeable non-saturating

Key concepts

Semimetallic Transport: This describes a material's electrical behavior where its electronic band gap closes, allowing charge carriers to move easily, similar to a metal but with some semiconducting features. In this alloy, Pt substitution causes the band gap to shrink near the Fermi level, leading to transport characteristics dominated by holes.
Power Factor (PF): The power factor is a crucial metric for thermoelectric materials that combines electrical conductivity and the Seebeck coefficient. A higher PF means the material is better at converting heat into electricity efficiently; this paper found it increased significantly after Pt alloying.
$zT$ Figure of Merit: $zT$ is a figure of merit used to rank thermoelectric materials, combining the power factor and temperature ($zT = rac{S^2 au}{ ho}$). A higher $zT$ indicates superior performance in converting heat to electricity, and the study found it improved from 0.114 (YNiBi) to 0.13 (YNi$_{0.5}$Pt$_{0.5}$Bi).
Hole-Dominated Conduction: This means that the electrical current is primarily carried by positive charge carriers, or 'holes,' rather than electrons. The Hall resistivity measurements confirmed this dominance, which is a key feature of the semimetallic transport observed in Pt-alloyed YNiBi.

Summary

The gist: Pt alloying transforms transport behavior towards a semimetallic state with holedominated conduction, a low hole carrier concentration of (1.9 × 1019 cm−3), and a sizeable non-saturating magnetoresistance of (18%) at 300 K under 14 T

Material Synthesis and Characterization

The study investigates the thermoelectric and magnetotransport properties of spark-plasma-sintered YNi0.5Pt0.5Bi The synthesis involved arc melting of high purity elements to form YNi0.5Pt0.5 ingots, which were then crushed, mixed with Bi pieces, and subjected to spark-plasma-sintering at a pressure of 70 MPa and a temperature of 650 °C to obtain pellets The elemental composition was determined using energy-dispersive X-ray spectroscopy (EDS) with a TESCAN Magna LMU system Structural characterization via powder Xray diffraction (XRD) confirmed the compound is single phase, yielding a lattice parameter of a = 6.541 Å The EDS measurements showed nearly one-third composition of Y and Bi elements, with approximately equal shares of Ni and Pt in composition

Electronic Transport Properties

The electrical resistivity exhibits temperature dependence similar to YPtBi but deviates from its perfectly linear behavior at low temperatures The Arrhenius equation, ρ = ρ0 exp Eg 2kBT, was used to calculate the energy band gap, Eg, which was found to be 0.049 eV DFT calculations confirmed the Pt-induced closing of the electronic band gap and a low density of states near the Fermi level, consistent with semimetal-like transport The Hall resistivity dependence showed a positive value for the Hall coefficient, indicating hole dominant transport in YNi0.5Pt0.5Bi The hole charge carrier density at 300 K was found to be 1.9 × 10 19 cm−3, and the hole charge carrier mobility at 300 K was found to be 255.8 cm 2V−1s−1

Magnetotransport Behavior

The magnetoresistance (MR%) for YNi0.5Pt0.5Bi was measured up to 14 T, yielding an MR% of 27% at 1.8 K, slightly decreasing with increase in temperature and becoming 18% at 300 K The MR behavior deviates from the perfectly linear behavior observed in YPtBi at low temperatures, suggesting the presence of multiple scattering mechanisms responsible for the magnetoresistance emergence Kohler scaling showed a linear dependence of ∆ρ/ρ0 with (B/ρ0) 1.5, but different temperature curves did not collapse onto a single curve The decrease in MR% at 14 T with increase in temperature has a linear relationship with decrease in hole mobility with increase in temperature

Thermoelectric Performance Metrics

The enhanced carrier effective mass together with the low carrier concentration results in an improved Seebeck coefficient of (130 µVK−1) The power factor (PF) attained a maximum value of 13.7 µW cm−1K−2 at 300 K, which is marginally higher to the value of 11.4 µW cm−1K−2 reported for YNiBi The figure of merit (zT) reached a value of 0.13 at 300 K, representing a clear improvement over pristine YNiBi The increasing trend of zT at 300 K suggests that YNi0.5Pt0.5Bi has the potential to exhibit even better thermoelectric performance at higher temperatures

Thermal Transport Analysis

The total thermal conductivity κ reached a local minima at ∼ 230 K with a value of 2.96 Wm−1K−1 The decrease in value of thermal conductivity of YNi0.5Pt0.5Bi at 300 K in comparison to YNiBi can possibly be due to rise in disorder in the lattice due to Ni and Pt mixing or addition of a relatively heavier element Pt

First-Principles Calculations

DFT calculations showed that the electronic band structure of YNi0.5Pt0.5Bi projected onto Pt orbitals indicates the closing of energy band gap The Fermi level crosses the valence band and conduction band at Γ and X high symmetry locations, with higher Pt orbital projection in both VBM and CBM at Γ and CBM at X The partial and total density of states around Fermi level for YNi0.5Pt0.5Bi depicts the closing of energy band gap and a low charge carrier density at Fermi level, further validating the experimental findings of low Sommerfeld coefficient value The results suggest a possibility of band inversion

Conclusion

In summary, Pt alloying transforms transport behavior towards a semimetallic state with holedominated conduction, a low hole carrier concentration of (1.9 × 10 19 cm−3), and a sizeable non-saturating magnetoresistance of (18%) at 300 K under 14 T The enhanced carrier effective mass together with the low carrier concentration results in an improved Seebeck coefficient of (130 µVK−1), while alloy-disorder-induced phonon scattering reduces the thermal conductivity Consequently, the room-temperature power factor and figure of merit reach 13.7 µWcm−1K−2 and 0.13, respectively, representing a clear improvement over pristine YNiBi The results of electronic band structure calculations of YNi0.5Pt0.5Bi showing the modification of the VBM and the CBM at Γ and X, just above the Fermi level, suggests a possibility of band inversion

Acknowledgments

K.M acknowledges financial support from the Max Planck Society under the Max Planck–India Partner Group Project; S.R acknowledges the Anusandhan National Research Foundation (ANRF), India, for support through the National Postdoctoral Fellowship under Grant No. PDF/2025/003558 The authors also acknowledge the Central Research Facility (CRF) and the Nanoscale Research Facility at IIT Delhi for providing access to materials characterization facilities, including PPMS, MPMS, EDX, and XRD measurements

References

1Z. K. Liu, L. X. Yang, S. C. Wu, C. Shekhar, J. Jiang, H. F. Yang, Y. Zhang, S. K Mo (2016)

2M M Hosen et al (2020)

3Y L Chen et al (2015)

4C Shekhar et al (2013)

5M Z Hasan and J E Moore (2011)

6N Xu Y Xu and J Zhu (2017)

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The hole charge carrier density is nearly constant upto ∼ 50 K, in the same temperature region, the resistivity value also has a small change with respect to the temperature The positive value of Seebeck coefficient also suggest the dominance of p-type charge carrier, which is in agreement with the Hall analysis The magnitude of S increases with increase in temperature, S increases from a value of ∼ 11.6 µVK−1 at 10 K to ∼ 130 µVK−1 at 300 K Assuming the single-parabolic-band assumption (SPB), the Seebeck coefficient, S, and Hall carrier density, nH, are used to calculate the carrier effective mass, m∗, at 300 K The value of scattering parameter (λ = 0) is used, assuming the carrier mobility to be limited by acoustic phonon scattering Assuming the carrier mobility limited by acoustic phonon scattering (λ = 0), and using S = 130 µVK−1 at 300 K in Eq. 1, the obtained values are η = 1.50, and F1/2(η) = 1.90 The Hall factor rH is calculated using Eq. 5 and obtained as 1.09 The effective mass of carrier, m∗, is obtained as 0.53 me using Eq. 3 with nH = 1.9 × 10 19 cm−3 at 300 K The Seebeck coefficient is much enhanced in comparison to the Seebeck coefficient reported as ∼ 90 µVK−1 at room temperature for YNiBi The Seebeck coefficient depends on the effective mass of charge carrier, m∗, and charge carrier concentration, n, by the relation, S ∝ m∗T/n 2/3

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The value of zT for YNi0.5Pt0.

Improvements for AI systems

The AI system can predict optimal alloying compositions for half-Heusler alloys by utilizing Pt alloying increases the room-temperature Seebeck coefficient from approximately 90 to 130 µVK−1 and The tuning of lattice parameter by mixing Ni and Pt will optimise the hybridisation strength to bring the conditions for desired band inversion.
The system can perform materials screening based on predicted thermoelectric performance by calculating the figure of merit (zT= 0.13) for candidate compounds, allowing prioritization of alloys with enhanced performance over pristine YNiBi.
The AI can analyze experimental data to infer electronic structure properties by correlating measured values like the low hole charge carrier density of 1.08×1019 cm−3 at 2 K with theoretical predictions regarding the semimetallic regime.
The system can predict magnetotransport behavior in novel alloys, specifically forecasting that "Pt alloying drives YNiBi toward semimetallic transport, characterized by hole-dominated conduction, a low Hall carrier concentration of 1.9×1019cm−3, and a sizeable nonsaturating magnetoresistance of 18% at 300 K under 14 T."
The AI can model the impact of structural modifications on thermal transport by predicting that alloy-disorder-induced phonon scattering reduces the thermal conductivity, enabling the design of materials with lower lattice thermal conductivity compared to baseline compounds like YNiBi.

Sources

Large linear magnetoresistance and weak anti-localization in Y(Lu)PtBi topological insulators