Anomalous metallic state in quasi-two-dimensional BaNiS\(_{2}\)

Abstract

We report on a systematic study of the thermodynamic, electronic and charge transport properties of high-quality single crystals of BaNiS\(_2\), the metallic end-member of the quasi-twodimensional BaCo\(_{1-x}\)Ni\(_x\)S\(_2\) system characterized by a metal-insulator transition at \(x_{cr}=0.22\). Our analysis of magnetoresistivity and specific heat data consistently suggests a picture of compensated semimetal with two hole- and one electron-bands, where electron-phonon scattering dominates charge transport and the minority holes exhibit, below \(\sim\)100 K, a very large mobility, \(\mu_h\sim\) 15000 cm\(^2\)V\(^{-1}\)s\(^{-1}\), which is explained by a Dirac-like band. Evidence of unconventional metallic properties is given by an intriguing crossover of the resistivity from a Bloch-Gr\"uneisen regime to a linear\(-T\) regime occurring at 2 K and by a strong linear term in the paramagnetic susceptibility above 100 K. We discuss the possibility that these anomalies reflect a departure from conventional Fermi-liquid properties in presence of short-range AF fluctuations and of a large Hund coupling.