Valency changes of Ce, Yb, and U in intermetallic compounds with Ni and Cu

The paper reports the results of studies of the valence states of Yb, Ce, and U in pseudo-binary compounds with Ni and Cu. The differences in electronegativities and electron densities between Yb, Ce, or U on the one hand and Ni or Cu on the other are such that in compounds with nickel the higher valence state prevails, while in compounds with copper the lower valence is dominant. Gradual replacement of Cu by Ni is expected to induce a valence change. The nature of this valence change has been studied in more detail by measuremnts of the concentration dependence of the lattice constants, while further information of the progress of the valence change was derived from results of magnetic measurements and from the results of resistivity measurements under applied pressure. 5 figures