Giant Nernst effect and field-enhanced transversal z(N)T 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 refrigerators. 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 = 100 K and B = 13 T, and the out-of-plane S-xy (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 rho(yy) in regard to B induces an almost linear increasing transversal z(N)T without saturation under high fields. The maximum z(N)T of 0.12 was obtained at B = 13 T and T = 120 K, which significantly surmounts its longitudinal counterpart under the same condition.