Thermodynamic and electronic properties of superconducting state of KM$_{\mathrm{2}}$ (M $=$ Sn, Pb) with the MgZn$_{\mathrm{2}}$-type structure

We discovered new superconductors of KM$_{\mathrm{2}}$ (M $=$ Sn, Pb) with the MgZn$_{\mathrm{2}}$-type (C14) structure (Laves phase) using the high pressure / temperature technique. The superconducting transition temperature ($T_{\mathrm{c}})$ is to be $T_{\mathrm{c}} \quad =$ 3.2 K for KSn$_{\mathrm{2}}$ and $T_{\mathrm{c}} \quad =$ 3 K for KPb$_{\mathrm{2}}$ (These samples include small impurity phase of Sn ($T_{\mathrm{c}} \quad =$ 3.7 K) and Pb ($T_{\mathrm{c}} \quad =$ 6.7 K)). In order to determine the superconducting parameters, we have performed the magnetic susceptibility measurement. The magnetization versus magnetic field curves of KM$_{\mathrm{2}}$ at 1.8 K shows a typical type-II superconducting behavior. From the density of state (DOS) calculation using the WIEN2K, the main contribution of DOS near the Fermi level ($E_{\mathrm{F}})$ is Sn (Pb) orbitals. In particular, $p$-orbitals of Sn (Pb) are dominant, indicating that the $p$-orbital of these atoms plays an important role for the superconducting state in KM$_{\mathrm{2}}$