THE TAMM SURFACE-STATE ON ORDERED CU3AU(001)

The Tamm surface state on Cu3Au(001) above the top of the bulk d-bands located at the center of the surface Brillouin zone (SBZ) has been ac curately characterized using angle-resolved photoemission. The propert ies of this state are very similar to those of the known Tamm states o n Cu(001) and Au(001). Its existence on Cu3Au(001) at 1.56 eV binding energy is in disagreement with published bulk band-structure calculati ons. Results of a new bulk electronic structure calculation for Cu3Au, based on the layer KKR and LMTO methods, are presented, which allow t he existence of the surface state at the observed energy.