  We analyze a model that accounts for the inherently large thermal lattice
fluctuations associated to the weak van der Waals inter-molecular bonding in
crystalline organic semiconductors. In these materials the charge mobility
generally exhibits a "metallic-like" power-law behavior, with no sign of
thermally activated hopping characteristic of carrier self-localization,
despite apparent mean-free-paths comparable or lower than the inter-molecular
spacing. Our results show that such puzzling transport regime can be understood
from the simultaneous presence of band carriers and incoherent states that are
dynamically localized by the thermal lattice disorder.
