Peak in the superconducting transition temperature of the nonmagnetic topological line-nodal material CaSb2 under pressure

Investigating the pressure dependence of the superconducting (SC) transition temperature ${T}_{\mathrm{c}}$ is crucial for understanding the SC mechanism. Herein, we report on the pressure dependence of ${T}_{\mathrm{c}}$ in the nonmagnetic topological line-nodal material ${\mathrm{CaSb}}₂$ based on measurements of electric resistance and alternating current magnetic susceptibility. ${T}_{\mathrm{c}}$ initially increases with increasing pressure and peaks at $\ensuremath{\sim}$ 3.1 GPa. With a further increase in pressure, ${T}_{\mathrm{c}}$ decreases and finally becomes undetectable at 5.9 GPa. Because no signs of phase transition or Lifshitz transition are observed in the normal state, the peculiar peak structure of ${T}_{\mathrm{c}}$ suggests that ${\mathrm{CaSb}}₂$ has an unconventional SC character.