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 semiconducting behavior. The main spectral feature is a pronounced zero-bias conductance minimum of about 10 meV width, which appears to be of magnetic nature. These break-junction experiments provide no clear-cut evidence for an energy (pseudo) gap in CeNiSn.