Electronic structure of icosahedral ${\mathrm{Al}}_{70}$${\mathrm{Pd}}_{20}$${\mathrm{Mn}}_{10}$

Photoemission spectroscopy measurements in the photon-energy range 35–150 eV have been used to determine the valence band of the stable icosahedral alloy ${\mathrm{Al}}_{70}$ ${\mathrm{Pd}}_{20}$ ${\mathrm{Mn}}_{10}$. Resonant photoemission near the Mn 3p→3d transition has been employed to show that the feature in the valence band at about 1.0 eV below the Fermi level is predominantly due to the Mn 3d-derived states. The effect of the Cooper minimum has been used to identify the feature at 3.6 eV below the Fermi level as being mainly due to states of Pd 4d character. The strong decrease of intensity towards the Fermi level has been interpreted as indicative of the presence 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 ${\mathrm{Al}}_{70}$ ${\mathrm{Pd}}_{20}$ ${\mathrm{Mn}}_{10}$ which could be ascribed to its quasiperiodic nature have been observed within the experimental resolution. A review of published experimental results on the electronic structure of quasicrystals obtained with techniques directly probing the occupied and unoccupied electronic states is also presented.