Physical properties of RBi2 (R=La,Ce) under pressure

We present a study of electrical transport properties of $R{\mathrm{Bi}}₂$ $(R=\mathrm{La},\mathrm{Ce})$ under hydrostatic pressure up to $\ensuremath{\sim}2.5$ GPa. These measurements are complemented by thermodynamic measurements of the specific heat on ${\mathrm{CeBi}}₂$ at different pressures up to 2.55 GPa. For ${\mathrm{CeBi}}₂$, 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 ${\mathrm{CeBi}}₂$ and ${\mathrm{LaBi}}₂$ show signatures of superconductivity for pressures above $\ensuremath{\sim}1.7$ GPa. However, the absence of superconducting features in specific-heat measurements for ${\mathrm{CeBi}}₂$ indicates that superconductivity in ${\mathrm{CeBi}}₂$ (and most likely ${\mathrm{LaBi}}₂$ as well) is not bulk and likely originates from traces of Bi flux, either on the surface of the platelike samples, or trapped inside the sample as laminar inclusions. Finally, we point out that extra caution should be exercised when claiming superconductivity based just on transport measurements, especially for Bi-containing compounds.