Mixed valence behavior in superconducting La1-xCexRu2 compounds

We have used X-ray absorption spectroscopy (XAS) to investigate the role pl ayed by cerium into driving the superconductor behavior in the La1-xCexRu2 solid solution. Trying to correlate the electronic changes detected by XAS with the magnetic and superconducting properties of these systems, we have also investigated the anomalous behavior of the low temperature transport p roperties of this series by measuring the resistivity down to 1.1 K, the ma gnetoresistance [0 < H < 2 T] and the heat capacity down to 4.7 K. These re sults are discussed in terms of the possible itinerant character of the Ce 4f electrons. (C) 1999 Elsevier Science B.V. All rights reserved.