Large Nernst effect and field enhanced transversal ZT in ZrTe5

Thermoelectric materials can recover electrical energy from waste heat and vice versa, which are of great significance in green energy harvesting and solid state refrigerator. The thermoelectric figure of merit (zT) quantifies the energy conversion efficiency, and a large Seebeck or Nernst effect is crucial for the development of thermoelectric devices. Here we present a significantly large Nernst thermopower in topological semimetal ZrTe5, which is attributed to both strong Berry curvature and bipolar transport. The largest in-plane S_xy (when B//b) approaches 1900 {\mu}V/K at T=100K and B=13T, and the out-of-plane S_xz (when B//c) reaches 5000 {\mu}V/K. As a critical part of z_N T, the linearly increased in-plane S_xy and resistivity \r{ho}_yy regard to B induces an almost linear increasing transversal z_N T without saturate under high fields. The maximum z_N T of 0.12 was obtained at B=13 T and T= 120K, which significantly surmounts its longitudinal counterpart under the same condition.