Enhanced Cryogenic Thermoelectricity in Semimetal Ta2PdSe6 through Non‐Fermi Liquid‐Like Charge and Heat Transport

Abstract The thermal properties of semimetal Ta2PdSe6 are studied, which exhibits a large thermoelectric power factor at low temperatures, by combining chemical substitution, transport measurements, and inelastic X‐ray scattering. A serious violation of the Wiedemann‐Franz law (WFL) is observed, which establishes the relationship between conductivity and thermal conductivity of metals. This violation leads to a thermal conductivity of Ta2PdSe6 lower than expected from the WFL and resistivity below 20 K, resulting in the highest figure of merit below 20 K among the p‐type thermoelectric materials thus far. Furthermore, electric and thermal resistivity show a non‐Fermi liquid‐like temperature dependence, indicating an exotic electronic state with an unconventional scattering process for heat and charge carriers. This study suggests that semimetals in the non‐Fermi liquid regime may be an intriguing platform, not only for fundamental physics but also for exploring novel thermoelectric materials tailored for low‐temperature applications.