XAFS study of the Ce valence in the intermetallic compounds Ce2Co17Si9 and Ce2Ni17Si9

We present an X-ray absorption spectroscopy study performed at the L-3 edge of cerium of two recently reported compounds Ce2Ni17Si9 and Ce2Co17Si9. The electronic valence state of cerium has been measured in both compounds and is discussed in the light of the local atomic environment. An intermediate valence stare of cerium previously proposed on the basis of neutron diffraction and magnetization measurements has been confirmed. This study has evidenced that the substitution of nickel for cobalt leads to a slight relocalization of the 4f states of cerium. Finally, the peculiar environment of cerium in this structure is compared to that of other intermetallic phases and is discussed in terms of Wigner Seitz cell volumes.