Conductivity of granular superconductors in a strong magnetic field

We suggest a theory of the negative magnetoresistance in a metallic granular superconductors. Calculations are performed in a strong magnetic field when the superconducting gap inside the grains is already destroyed by orbital mechanism. We found that even without including the effects of weak localization the conductivity of granular system strongly decreases due to reduction of the density of states by superconducting fluctuations. At the same time, it is shown that Aslamazov-Larkin and Maki-Thompson corrections Vanish at very low temperatures. Our results can explain the unusual experimental behaviour of the resistivity of granular system in a strong magnetic field.