ANGLE-RESOLVED PHOTOEMISSION EXPERIMENTS ON BI2SR2CACU2O8- EFFECTS OFTHE INCOMMENSURATE LATTICE MODULATION(DELTA(001) )

Core-level X-ray photoelectron-diffraction patterns have been measured from cleaved Bi2Sr2CaCu2O8+delta (001) surfaces for all elements pres ent in this compound. The incommensurate modulation along b ([010]) le ads to a strong inequivalence of a- and b-directions for Bi, Sr and Cu photoelectrons, while Ca and O emission show less effect. Ultraviolet -photoemission experiments recording the emission intensity at the Fer mi energy over a large solid angle are also presented, providing a dir ect mapping of the Fermi surface. A c(2 x 2) superstructure is observe d on the Fermi surface suggesting antiferromagnetic correlations withi n the Cu-O planes. The effects of the lattice modulation are clearly o bservable at the Fermi energy, and they are enhanced for binding energ ies higher than a few tens of meV.