[en] Full text: Bimetallic surfaces have attracted considerable interest due to their catalytic, electronic, electrochemical, and magnetic properties. The deposition of an ultra-thin metal film on a single crystal metal substrate can produce a bimetallic surface. Films comprised of transition and noble metals are of particular interest in heterogeneous catalysis, since bimetallic surfaces have shown enhanced activity for catalytic reactions as compared to pure metals. While Pd is an excellent catalyst for many reactions, Au alone is considered as a poor catalyst, however, the activity and selectivity of Pd catalysts can be significantly enhanced by the addition of Au. Au and Pd are completely miscible in all proportions and there is only a slight lattice mismatch (less than 5%) between Au(111) and Pd(111) surfaces. Thus pseudomorphic overlayers of Pd on Au(111) and Au on Pd(111) can be prepared. In this work, ultra-thin films of Au were deposited on the Pd(111) surface in ultra-high vacuum and then characterized by X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), and X-ray photoelectron diffraction (XPD) generated by synchrotron radiation. LEED shows a (1 X 1) pattern similar to that of the substrate. XPS results suggest that Au does not diffuse into the bulk. The comparisons between experimental and theoretical XPD results indicate that the Au film is 6 ML thick. (author)