We have studied magnetoresistance in thin films of amorphous indium oxide with various degrees of oxidation, i.e., with various densities of states in the velocity of the Fermi level. A large negative magnetoresistance is observed when the films are in the insulating state. The negative field derivative dRIdH of the resistance persists up to 20 T, the highest magnetic field in our experiment. The magnetoresistance is described in terms of a field-dependent gap at the Fermi level. Such a gap can arise due either to tunneling in a system of fluctuation-induced superconducting clusters or to the Cooper interaction between electrons localized in shallow minima of the random potential. In the latter case, if the depth of the minima is smaller than the Debye energy, the electrons are virtually delocalized by short-wavelength phonons.
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