Breakdown of Wiedemann–Franz Law and Large Transverse Thermoelectric Conductivity in the Topological Semimetal, TaSb2

The Wiedemann–Franz (WF) law, a hallmark of Fermi liquid theory, links electrical and thermal conductivities in metals via the Lorenz number. Deviations from this law are often a sign of unconventional quasiparticle behaviors, a phenomenon increasingly observed in topological semimetals (TSMs). TSMs with their unique electronic structures are particularly promising for transverse thermoelectric (TE) applications. Here, we investigate the magneto-TE properties of polycrystalline TaSb2, a compensated topological semimetal. Our measurements reveal a substantial breakdown of the WF law, with the Lorenz number dropping below the Sommerfeld value above 40 K, indicating non-Fermi liquid behavior. TaSb2 exhibits a pronounced transverse thermoelectric response, characterized by a peak Nernst thermopower of ∼37 μV K–1 at 25 K under a 9 T field, far exceeding the Seebeck response. The corresponding Nernst power factor reaches 10.4 × 10–4 W m–1 K–2, with an average value of 1.8 × 10–4 W m–1 K–2 across the measured temperature range, more than seven times the average Seebeck power factor. Additionally, the transverse thermoelectric conductivity αyx peaks at ∼30 A m–1 K–1 at 30 K. These results underscore the promise of polycrystalline TaSb2 as a high-performance, low-temperature transverse thermoelectric material with practical scalability, paving the way for future magnetically enhanced solid-state cooling technologies.