  We have investigated break junctions of normal non-magnetic metals as well as
ferromagnets at low temperatures. The point contacts with radii 0.15 - 15 nm
showed zero-bias anomalies which can be attributed to Kondo scattering at a
single Kondo impurity at the contact or to the switching of a single conducting
channel. The Kondo temperatures derived from the width of the anomalies varied
between 10 and 1000 K. These results agree well with literature data on
atomic-size contacts of the ferromagnets as well as with spear-anvil type
contacts on a wide variety of metals.
