59.1 Introduction Graphite intercalated compounds (GICs) are natural two-dimensional (2D) electronic systems in which carriers move mainly in parallel to the direction of the graphite planes. During the intercalation process there is a transfer charge from intercalate molecules to graphite layers and layers of graphite enriched with additional charge carriers. In this process, halogens and halides act as electronic acceptors, enriching the graphite layer with additional delocalized holes. Redistribution of charge between the layers of graphite and intercalate layers causes the formation of a charged layer of intercalate that contains localized electrons and acts as an electrostatic screen between the graphite layers on both sides of the intercalate layer. This high potential barrier prevents the movement of charge carriers through the intercalate layer perpendicular to the layers of graphite. The 2D properties of GICs arise from the existence of the charged intercalate layer with localized electrons. Thus, a charge carrier system in low-stage GICs is a degenerate 2D electron gas. The two-dimensionality of such electron gas is associated with structural features of the electronic structure of GICs. GICs are a perfect model to study the physical properties of 2D structures. A number of physical phenomena were investigated in acceptor GICs. Thus, the literature contains data on the study of charge carrier phonon drag, which for GICs based on high oriented pyrolitic graphite (HOPG) is manifested in a wide temperature range up to room temperature [1-4].
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