VALENCE STATES OF YB IN YB5SI3

We have measured the quadrupole hyperfine interaction in the intermeta llic compound Yb5Si3 using Yb-170 Mossbauer absorption spectroscopy in the temperature range 0.03-80 K and Yb-172 perturbed angular correlat ion spectroscopy in the temperature range 20-750 K. Data of L-III-edge x-ray absorption and magnetic susceptibility are also presented, as w ell as a Yb-170 Mossbauer spectrum with a magnetic field of 7 T at 4.2 K. There are two distinct crystallographic sites for Yb in Yb5Si3. Th e whole set of our measurements shows that the two sites contain Yb io ns in a charge state close to 3+, but with different hybridization str engths, making Yb5Si3 a unique compound. No magnetic ordering of the Y b3+ sublattice is shown down to a temperature of 0.03 K.