The diffusion of a charged light impurity between the layers of such a crystal was considered. The main mechanism which governed the diffusion process was assumed to be interaction with a Fermi gas of electrons that was localized in neighboring layers.

V.K.Dugaev, P.P.Petrov: Fizika Tverdogo Tela, 1995, 37[2], 318-23 (Physics of the Solid State, 1995, 37[2], 173-5)