CHANGE OF THE YB VALENCE IN YB-TM-AL COMPOUNDS

We present an investigation of Yb-TM-Al phase diagrams with TM = Pd, A g and Au. Several new compounds have been characterized by measurement s of the magnetic susceptibility, the electrical resistivity and, in s ome cases, the specific heat. It seems that the crossover from the sta ble-trivalent to the intermediate-valent behavior occurs much more abr uptly in Yb- than in Ce-based compounds on changing the composition. A comparison of the Ce-TM-Al compounds with their Yb homologs suggests that replacement of Ce by Yb in an intermediate-valent Ce compound and in a trivalent Ce compound results in an Yb3+ and in an Yb2+ state, r espectively.