Break-junction experiments on the Kondo semiconductor CeNiSn: tunnelling versus direct conductance

The rare-earth Kondo semiconductor CeNiSn is investigated by point-contact and tunneling spectroscopy using mechanically controllable break junctions. I(V) characteristics and their derivatives are recorded for contacts from the metallic to the tunneling regime at temperatures between 0.1-8 K and in magnetic fields up to 8 T. It is found that CeNiSn behaves like a compound with typical metallic properties instead of exhibiting the expected semico nducting behavior. The main spectral feature is a pronounced zero-bias cond uctance minimum of about 10 meV width, which appears to be of magnetic natu re. These break-junction experiments provide no clear-cut evidence for an e nergy (pseudo) gap in CeNiSn. (C) 2000 American Institute of Physics. [S106 3-777X(00)01007-0].