The electronic structure of A170Ni15Co15 decagonal quasi-crystal has been studied by X-ray photoelectron spectroscopy (XPS). The disappearance of the Ni2p(3d9) satellite and the decreased intensity of the 3F state in the Ni-L3M45M45 Auger spectra indicate a strong d-sp hybridization accompanied by the filling of the Ni3d bands. The filling of the Ni3d bands produces closed-shell type XPS spectra of the Ni core lines, while Co core line XPS spectra show that a significant amount of d holes are still localized on Co. This picture suggests that the magnetic properties are mainly determined by Co. The dispersion of the 3d holes is also responsible for the drop of the 3d states near E(F) but the angle integrated density of states does not exhibit a pseudo-gap. Finally, the correlation energy, U(A), has been calculated from the kinetic energy of the 1G term of the Ni-L3M45M45 Auger emission.
