A negative thermal expansion in the layers in layered semiconductors GaSe and InSe are found.

For the first time an explanation of negative thermal expansion in the plane of the classic layered crystal - graphite on the basis of the so-called "membrane" effect are given.

An interpretation of the observed effect of "thermal anomalies" in thermal conductivity in graphite, in which the temperature increase in the heat ahead of the temperature increase of heat capacity are proposed.

Anomalies in the temperature dependence of thermal expansion in layered semiconductors TlGaSe₂ and TlInS₂ in area of phase transitions were found. From studies of the effect of preliminary illumination and applied external electric field on thermal expansion and TlGaSe₂ and TlInS₂ concluded that the essential role of the electronic subsystem in thermal expansion.

Abdullayev N.A. investigate the features of the mechanism of charge transfer in-plane and in a direction perpendicular to the layers in a wide range of layered crystals - semiconductors, semimetals, and metals.

It is shown that in a layered semiconductor InSe while in-plane charge transport occurs in extended states in a direction perpendicular to the layers - by electron hopping between localized states lying in a narrow band of energies near the Fermi level. A similar case occurs in the most typical layered crystal - graphite.