ELECTRONIC-PROPERTIES OF QUASI-CRYSTALS

Spectroscopic measurements performed on quasicrystals and related crys talline phases show a well defined pseudo-gap near the Fermi level and indicate a strong sp-d hybridisation. These results give good support to an analogy between quasicrystals and Hume-Rothery alloys. Electron ic transport measurements are also presented. The conductivity is very low (approximately 100 (OMEGAcm)-1) indicating the proximity of a met al-insulator transition and has a unusual behaviour for a metallic sys tem. The interpretation of these results in a classical band picture s eems difficult and we propose an explanation based on the existence of peculiar electronic states in quasicrystals, the so-called critical s tates. The conductivity is interpreted by electronic hopping between s tructural entities separated by about 30 angstrom.