Magnetoresistance of granular superconducting metals in a strong magnetic field

The magnetoresistance of a granular superconductor in a strong magnetic fie ld is considered. It is assumed that this field destroys the superconductin g gap in each grain, such that all interesting effects considered in the pa per are due to superconducting fluctuations. The conductance of the system is assumed to be large, which allows us to neglect all localization effects as well as the Coulomb interaction. It is shown that at low temperatures t he superconducting: fluctuations reduce the one-particle density of states but do not contribute to transport. As a result, the resistivity of the nor mal state exceeds the classical resistivity approaching the latter only in the limit of extremely strong magnetic fields, and this leads to a negative magnetoresistance. We present detailed calculations of physical quantities relevant for describing the effect and make a comparison with existing exp eriments.