Anisotropic Superconducting Properties of MgB 2 and Related Compounds

Anisotropic superconducting properties of inter-metallic compounds MgB 2 , Y 2 PdGe 3 , and CaAlSi with AlB 2 structure are studied by detailed angular dependent transport measurements. MgB 2 and CaAlSi shows appreciable anisotropy of the upper critical field, H c 2 , with mass anisotropy parameter γ=3 and 2, respectively, while Y 2 PdGe 3 is almost isotropic. In-plane anisotropy of H c 2 in these hexagonal superconductors is very small, consistent with the prediction based on GL theory.