The thermal conductivity κ(B,T) of polycrystalline superconducting MgB2 was studied as a function of temperature (from 4 up to 50K) and (up to a rather large 14T) applied magnetic field. No anomaly in the thermal conductivity κ(B,T) was observed around the superconducting transition in the absence or presence of magnetic fields up to 14T; at that field value the superconductivity of MgB2 persisted. The thermal conductivity in zero field shows a T-linear increase up to 50K. The thermal conductivity was found to increase with increasing field at high fields. The results were interpreted as if there were 2 sub-systems of quasiparticles with differing field-dependent characters in a two- (L- and S-) band superconductor reacting differently with the vortex structure. The unusual enhancement of κ(B,T) at low temperature but higher than a (BC2S  3T) critical field was interpreted as a result of the overlap of the low energy states outside the vortex cores in the S band. An order of magnitude of the BC2S temperature dependence was given, in agreement with recent results by other authors under different experimental conditions

Two-Bandgap Magneto-Thermal Conductivity of Polycrystalline MgB2. B.M.Wu, D.S.Yang, W.H.Zeng, S.Y.Li, B.Li, R.Fan, X.H.Chen, L.Z.Cao, M.Ausloos: Superconductor Science and Technology, 2004, 17, 1458-63