Superconductivity in ternary silicide NaAlSi with layered diamond-like structure

We have succeeded in synthesizing a new member of ternary silicide NaAlSi with a superconducting transition temperature Tc−onset = 7 K by high pressure technique. The crystal structure of NaAlSi is the layered diamond-like structure with a space group of P4/nmm (no. 129, Z = 3) and without inversion symmetry. The superconducting properties in NaAlSi have been investigated by means of DC and AC magnetic susceptibility measurements. These magnetic responses indicate that NaAlSi belongs to a conventional type-II superconductor with a Ginzbrug–Landau parameter κ = 13.8. From the band structure calculations, we found that the hole band of Si p- and electron Al s-orbitals play an important role for the superconductivity in this system.