Pressure study of the noncentrosymmetric 5d-electron superconductors CaMSi3 (M= Ir, Pt)

We report hydrostatic pressure study on the Rashba-type noncentrosymmetric superconduc- tors CaMSi3 (M= Ir, Pt). The temperature dependence of the resistivity for both compounds is well described by the conventional Bloch-Gr"uneisen formalism at each pressure. This fact suggests that electron-phonon scattering is dominant in these compounds. The superconducting critical temperature Tc decreases by pressure as \sim 0.2 K/GPa above 0.41 GPa to 2 GPa for both compounds. This behavior of Tc can be explained with a modest decrease of the density of states based on the conventional BCS theory.