Giant isotropic Nernst effect in an anisotropic Kondo semimetal

TL;DR

This study investigates the Nernst effect in CeNiSn, revealing an isotropic large Nernst signal despite anisotropic magnetotransport, supporting the presence of an isotropic Fermi surface with anisotropic quasiparticle mass.

Contribution

The paper provides experimental evidence that challenges the assumption of a nodal metal origin for anisotropic transport in CeNiSn, suggesting instead an isotropic Fermi surface with anisotropic mass.

Findings

Large Nernst signal is isotropic despite anisotropic Hall conductivity.

Results support an isotropic Fermi surface with anisotropic quasiparticle mass.

Findings challenge the idea that anisotropic transport is due to a nodal metal.

Abstract

The "failed Kondo insulator" CeNiSn has long been suspected to be a nodal metal, with a node in the hybridization matrix elements. Here we carry out a series of Nernst effect experiments to delineate whether the severely anisotropic magnetotransport coefficients do indeed derive from a nodal metal or can simply be explained by a highly anisotropic Fermi surface. Our experiments reveal that despite an almost 20-fold anisotropy in the Hall conductivity, the large Nernst signal is isotropic. Taken in conjunction with the magnetotransport anisotropy, these results provide strong support for an isotropic Fermi surface with a large anisotropy in quasiparticle mass derived from a nodal hybridization.