Superconducting high pressureCaSi2phase withTcup to 14 K

We have studied the occurrence of superconductivity under pressure in the ${\mathrm{CaSi}}_2$ family of compounds, namely the semimetallic trigonal phase and the $\alpha -{\mathrm{ThSi}}_2$-type tetragonal one. Although only the latter is superconducting ${(T}_c=1.56\mathrm{}\mathrm{K})$ at ambient pressure, starting from the trigonal phase and applying high pressure (>12 GPa) we have found a new superconducting phase with $T_c^{\mathrm{onset}}\sim 14\mathrm{K},$ among the highest ever found in silicon based materials.