ELECTRONIC-STRUCTURE OF ICOSAHEDRAL AL70PD20MN10

Photoemission spectroscopy measurements in the photon-energy range 35- 150 eV have been used to determine the valence band of the stable icos ahedral alloy Al70Pd20Mn10. Resonant photoemission near the Mn 3p --> 3d transition has been employed to show that the feature in the valenc e band at about 1.0 eV below the Fermi level is predominantly due to t he Mn 3d-derived states. The effect of the Cooper minimum has been use d to identify the feature at 3.6 eV below the Fermi level as being mai nly due to states of Pd 4d character. The strong decrease of intensity towards the Fermi level has been interpreted as indicative of the pre sence of a pseudogap at the Fermi level. However, it is shown that the Fermi cutoff also contributes to the observed intensity decrease. No unusual features in the valence band of icosahedral Al70Pd20Mn10 which could be ascribed to its quasiperiodic nature have been observed with in the experimental resolution. A review of published experimental res ults on the electronic structure of quasicrystals obtained with techni ques directly probing the occupied and unoccupied electronic states is also presented.