Large Nernst effect and possible temperature-induced Lifshitz transition in topological semimetal YbMnSb2

Topological materials provide an interesting platform in the study of thermoelectric effect due to their novel electronic properties. Here we report the magneto-Seebeck (MS) effect, large Nernst effect, and a possible temperature-induced Lifshitz transition in topological semimetal YbMnSb2. It exhibits evident quantum oscillations in the MS effect from which six frequencies are extracted and a light effective mass of F4 is obtained. The large Nernst effect with the Nernst thermopower of about 40 & mu;VK-1 is discovered around 120 K and 14 T. Combining the analysis of the first-principles calculations and the Hall effect, we suggest that the large Nernst signal could mainly stem from the Dirac bands-induced high mobility and small Fermi energy (& epsilon;F). Besides, it could be further enhanced by the modified carrier properties resulting from the temperature-induced Lifshitz transition through the so-called ambipolar effect.