Thermoelectric scaling laws and Mott relation breakdown in the field-induced Weyl metallic state of Bi1-xSbx (x ~ 3-4 %)

The Mott relation in thermoelectricity is widely regarded as a universal law, holding across diverse systems as long as quasiparticles exist. Its resilience has made it central to understanding how electrical and thermal currents are linked in quantum materials. Here we test its validity in antimony-doped bismuth (Bi _1−x Sb _x , x ~ 3–4%) single crystals, which host a Weyl metallic state near a topological critical point. Magneto-Seebeck and anomalous Nernst measurements confirm the chiral anomaly, after which we propose a modified Mott relation that incorporates thermal broadening. This framework reveals a linear scaling between longitudinal and transverse thermoelectric conductivities. Unexpectedly, the scaling collapses for the anomalous transverse response, leaving no thermoelectric scaling law. Our findings establish Bi _1−x Sb _x as a rare case of Mott relation breakdown, exposing the limits of this universal law and demanding new theoretical approaches to transport in topological systems.