Figure 1: Thermopower and Nernst effect in a topological crystalline insulator.

The panels provide an overview of how the thermopower S_xx and Nernst signal S_xy vary with field B in a high-mobility crystal (sample 1) of Pb_1−xSn_xSe with x=0.23. (a, b) Curves of S_xx versus B at selected T (sample 1). At each T, the V-profile bracketing B=0 reflects the rapid crossover from small μB to large μB regime. (c) The Nernst signal S_xy/T from 60 to 300 K. The sharp peaks reflect the semiclassical response. An anomalous sign change occurs at T_inv=180 K. (b,d) Fits equations 1 and 2 (thin curves) to S_xx and S_xy at low B. For S_xy (d), we have had to invert the sign. At 30.3 K, the best-fit values of μ, and _H are 51,404 cm² V⁻¹ s⁻¹, 61.5 eV⁻¹ and 104.6 eV⁻¹, respectively. At 4.71 K, the corresponding values are 113,250cm² V⁻¹ s⁻¹, 52.3 eV⁻¹ and 81.3 eV⁻¹. The inset shows the L (111) points on the hexagonal faces of the Brillouin Zone.