Superconductivity in Ba2/3Pt3B2 with the Kagome lattice

Resistivity, magnetization and low temperature specific heat (down to 0.4 K) of Ba2/3Pt3B2 with the Kagome lattice of the transition metal Pt atoms have been investigated. The magnetization hysteresis loops measured on the sample indicate that it belongs to a type-II superconductor. The specific heat exhibits ΔC/γnT|Tc≈1.7ΔC/γnT|Tc≈1.7, showing a moderate coupling superconductivity. Furthermore, the magnetic field dependence of the electronic specific heat coefficient in the low temperature limit demonstrates a linear relation γe∝Hγe∝H, suggesting an s-wave gap. Surprisingly, the Wilson ratio determined here is about 34, which may be explained by short range magnetic correlation. Compared with the compound LaRu3Si2, we intend to attribute the extraordinarily large Wilson ratio to the deficiency of Ba atoms. Further theoretical and experimental efforts are required to clarify this issue.