It was recalled that a simple BCS model with an anisotropic s-wave order parameter had been proposed which accounted for available thermodynamic and scanning tunneling microscopy data from polycrystalline MgB2. Here, a further investigation was made of this theory by calculating the temperature dependence of the thermal conductivity, the nuclear spin relaxation rate, and the angular dependence of the upper critical field.

Properties of Anisotropic s-Wave Superconductivity in MgB2. Y.Chen, S.Haas, K.Maki: Current Applied Physics, 2001, 1[4-5], 333-6