Physical properties of $R$Bi${}_2$ ($R=$La, Ce) under pressure

Abstract

We present a study of electrical transport properties of $R$Bi${}_2$ ($R$ = La, Ce) under hydrostatic pressure up to $\sim$ 2.5 GPa. These measurements are complemented by thermodynamic measurements of the specific heat on CeBi${}_2$ at different pressures up to 2.55 GPa. For CeBi${}_2$, we find a moderate increase of the antiferromagnetic transition, $T_{\text{N}}$, from 3.3 K to 4.4 K by pressures up to 2.55 GPa. Notably, resistance measurements for both CeBi${}_2$ and LaBi${}_2$ show signatures of superconductivity for pressures above $\sim$ 1.7 GPa. However, the absence of superconducting feature in specific heat measurements for CeBi${}_2$ indicates that superconductivity in CeBi${}_2$ (and most likely LaBi${}_2$ as well) is not bulk and likely originates from traces of Bi flux, either on the surface of the plate-like samples, or trapped inside the sample as laminar inclusions.