Revisiting the physical properties of Ce2Ru3Ga9: Intermediate valence, or Kondo lattice system?

In this paper we discuss in details the experimental results regarding to the crystal structure, magnetic, electronic and thermal transport properties of the strongly correlated compound Ce2Ru3Ga9. Based on these data we report the observation of coexistence and competition between intermediate valence state on Ce ions and Kondo-like behaviour in a high-quality polycrystalline alloy. Intermediate valence behaviour manifests itself in the temperature dependence of the magnetic susceptibility (χ), which reveals a broad maximum at around 335 K as is frequently observed for Ce compounds with mixed-valent Ce3+/4+. The electrical resistivity (ρ) behaves in a manner characteristic of systems with strong electronic correlations. First varies in a metallic manner, typical for intermediate valence compounds and than demonstrating a behaviour pointing on the onset of coherence that develops above the room temperature. The thermoelectric power (S) shows a broad maximum with a relatively large value of Smax  = 35.7 μV/K, which is typical for the Ce-based systems that exhibit a strong c−f hybridization. Both ρ(T) and S(T) show the −lnT behaviour at high temperatures thereby indicating on the presence of incoherent electron scattering on a local moment of Ce3+. Moreover, a particular attention has been paid to the low-T behaviour in the investigated physical quantities, as it is one of the focuses of this paper.