Intermediate Valence of CeNi2Al3 Compound and Its Evidences: Theoretical and Experimental Approach

We present measurements of magnetic, transport and electronic properties obtained for polycrystalline CeNi2Al3 intermetallic compound. Magnetic susceptibility chi(T) was investigated in the range from 2 to 700 K, and its behavior is characteristic of a compound with unstable valence, varying between Ce3+ and Ce4+. In the temperature range down to 2 K there was no trace of magnetic order, no anomalies in the temperature dependence of the specific heat were found. The Sommerfeld coefficient extracted from the linear term of the heat capacity takes a value of gamma = 21 mJ/(mol K-2). The dependence of S(T) is linear up to about 25 K, which is symptomatic of a thermopower in the Fermi's liquid regime. The structure of satellites in the Ce(3d) electron spectrum obtained by the X-ray photoelectron spectroscopy (XPS) method indicates that the states of Ce(4f) are of mixed valence character. Analysis of Ce(3d) states based on Gunnarsson-Schonhammer theory shows that the energy of hybridization of Ce(4f) states with a conduction band is about 78 meV. For more detailed information about electronic states the fully relativistic band structure was calculated within the density functional theory (DFT) for the first time. Below Fermi's energy, the density of states is mainly formed by Ni(3d) states hybridized with Ce(4f) ones.