Measurement of the thermopower anisotropy in iron arsenide

•In this study, in order to investigate the origin of the in-plane anisotropy, the in-plane anisotropy of the thermopower was measured for the detwined single crystals of BFe2As2. And, we found no anisotropy in the thermopower above TAFO, although there is a large anisotropy in the resistivity. This result gives evidence that the anisotropy in the resistivity arise from the anisotropy of the scattering time, and the energy dependence of the scattering time can be considered negligible. In the case of iron pnictides, the proposed orbital ordering more likely results in an anisotropy of electronic structure below TAFO, whereas the spin-nematic ordering leads to an anisotropy of electron scattering above TAFO. Therefore, our results suggest that nematicity above TAFO results from anisotropic magnetic scattering. We investigated the in-plane anisotropy of the thermopower and electrical resistivity on detwinned single crystals of BaFe2As2. The in-plane anisotropy of the resistivity was clearly observed far above the magnetostructural transition temperature TAFO. While, the thermopower showed the in-plane anisotropy only below TAFO. These results are associated with the different origin of the anisotropy above and below TAFO. Since the thermopower does not depend on the scattering time, the anisotropy of the resistivity above TAFO is considered to be due to the anisotropic scattering. On the other hand, the anisotropy in the thermopower below TAFO is ascribed to the reconstructed Fermi surface.