Alloying effects on the 1G(0) (single-atom) contact of An has been investigated for four solute elements, Ag, Cu, Pt, and Pd, under bias voltages from 0.2 to 1.0 V We found that the alloying appreciably affects the formation probability p of the I Go contact, but makes little influence on the average 1G(0) plateau length . The latter observation strongly suggests that the 1G(0) contact of Au alloys consists of Au atom(s), with no solute atoms participating into the contact. On the other hand, the alloying effect on p was found to be element-dependent. Pd and Pt solutes give rise to a rapid suppression of p with increasing the bias, while the alloying with Cut and Ag yields weak bias dependence of p, which is not much different from that of pure An. (C) 2003 Elsevier B.V. All rights reserved.