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The cerium effective valence was investigated by means of CeL 3 -XANES spectroscopy in some intermediate valence Ce-based systems with different magnetic ordering mechanisms: CeNi doped with Nd, Pr and Gd in the temperature range 5-300 K, and Ce 2 Fe 17-x Mn x intermetallics. The dependences obtained are considered within the frames of generally accepted mechanisms of rare-earth ions intermediate valence states. Possible correlations between the cerium effective valence and the magnetic properties of compounds are also noted.

CePt3Si exhibits antiferromagnetic order at T N ≈ 2.2 K and superconductivity (SC) at T c ≈ 0.75 K. Large values of H′ c2 ≈ −8.5 T/K and H c2(0) ≈ 5 T indicate Cooper pairs formed out of heavy quasiparticles. The mass enhancement originates from Kondo interaction with a characteristic temperature T K ≈ 8 K. NMR and μSR measurements evidence coexistence of SC and long-range magnetic order on a microscopic scale. Moreover, CePt3Si is the first heavy-fermion SC without an inversion symmetry. This gives rise to a novel type of the NMR relaxation rate 1/T 1 never reported before for other heavy-fermion superconductors. Studies of Si/Ge substitution allow us to establish a phase diagram.