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Here, we investigate the thermoelectric properties of the marcasite-type compounds MSb₂ (M = Ta, Nb) in the temperature range of 310-730 K. These compounds were synthesized by a solid-state reaction followed by the spark plasma sintering process. The Rietveld refinement method confirms the monoclinic phase with space group C2/m for both compounds. The observed values of Seebeck coefficients exhibit non-monotonic behaviour in the studied temperature range, with the maximum magnitude of −14.4 and −22.7 µV ^-1for TaSb₂and NbSb₂, respectively at ∼444 K. The negative sign of S in the full temperature window signifies the n-type behaviour of these compounds. Both electrical and thermal conductivities show decreasing trends with increasing temperature. The experimentally observed thermoelectric properties are understood through the first-principles DFT and Boltzmann transport equation. A pseudogap in the density of states around the Fermi level characterizes the semimetallic behaviour of these compounds. The multi-band electron and hole pockets were found to be mainly responsible for the temperature dependence of transport properties. The experimental power factors are found to be ∼0.09 and ∼0.42 mW m^-1 K^-2 at 300 K for TaSb₂and NbSb₂, respectively. We found that there is much room for improvement of power factor by tuning carrier concentration. The DFT-based calculations predict the maximum possible power factors at fairly high doping concentrations. The present study suggests that the combined DFT and Boltzmann transport theory are found to be reasonably good at explaining the experimental transport properties, and moderate power factors are predicted.

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• Creative Commons BY-NC-ND Attribution-NonCommercial-NoDerivs 4.0 International
  

  This is the Accepted Manuscript version of an article accepted for publication in Journal of Physics: Condensed Matter. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://dx.doi.org/10.1088/1361-648X/adb409.

Keyword: Thermoelectric properties, density functional theory, electronic structure, electron and hole pockets, semi-classical Boltzmann theory, power factor

Date published: 2025-03-31

Publisher: IOP Publishing

Journal:

• Journal of Physics: Condensed Matter (ISSN: 09538984) vol. 37 issue. 13 135701

Funding:

• Japan Science and Technology Corporation JPMJMI19A1

Manuscript type: Author's version (Accepted manuscript)

MDR DOI: https://doi.org/10.48505/nims.5332

First published URL: https://doi.org/10.1088/1361-648x/adb409

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Updated at: 2026-02-18 12:30:04 +0900

Published on MDR: 2026-02-18 09:29:33 +0900