It is shown that the conductivity of granular metals on the insulating side of the metal-insulator transition can be essentially determined by intergrain tunnelling via virtual localized states of intermediate grains. This mechanism gives rise to the temperature dependence of the conductivity in the form ln sigma approximate to constant - (T-0/T)(x), where x approximate to 0.4, and to a large enhancement of the conductivity. [References: 33]
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