The features of thermal properties and CEF-influence in intermediate valence compound CeB4 at the temperatures of 2-300Â K

Heat capacity and lattice parameters of cerium tetraboride were experimentally determined at 2 - 300 K. An anomalously large contribution of free electrons to the heat capacity was influenced by Fermi liquid state in the cerium boride. The parameters of Einstein and Debye contributions to CeB4 heat capacity, as well as free electron gas contribution and Schottky heat capacity have been determined. A negative thermal expansion (NTE) of CeB4 was found (5-25 K). We were not able to explain the NTE by the influence of intermediate valence of cerium ions. The NTE was attributed to the influence of the crystal electric field (CEF) on Ce3+ ions.