Nb atoms on the surface of Ag, an unexpected Kondo system

Recently Lang et al. [P.Lang et al., Solid State Commun. 92, 755 (1994)] predicted that 4d and 5d atoms may become magnetic when they occupy a surface position on a Ag (100) surface.-In this paper we investigate the properties of Nb atoms on the surface of Au and Ag, a particularly interesting choice, because Nb is a good bulk superconductor. Our experimental method is quantum interference or weak localization, which is extremely sensitive to magnetic scattering. Our results are that Nb on the surface of Au is nonmagnetic while on the surface of Ag it behaves as a Kondo impurity with a Kondo temperature considerably above 20 K.