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

## TL;DR

This study investigates the electrical and thermodynamic properties of $R$Bi$_2$ ($R$=La, Ce) under pressure, revealing signatures of non-bulk superconductivity likely due to Bi flux traces, and a pressure-induced increase in antiferromagnetic transition temperature for CeBi$_2$.

## Contribution

First detailed pressure-dependent transport and thermodynamic measurements on $R$Bi$_2$ compounds, clarifying the nature of observed superconductivity and magnetic transitions.

## Key findings

- Superconductivity signatures appear above 1.7 GPa in resistance measurements.
- No bulk superconductivity detected in specific heat measurements.
- Antiferromagnetic transition temperature of CeBi$_2$ increases with 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.