Electronic properties of stable quasicrystals: towards a semiconducting quasicrystal?

Anomalous transport properties are presented of a series of pure AlCuFe icosahedral phases of very high structural quality including a millimetre size single grain. The most salient feature is that all these metallic samples present very high resistivity values close to the metal-insulator transition (MIT) rising up to 10 000 μΩ cm at 4 K in Al_62.5Cu₂₅Fe_12.5. The resistivity at 4 K depends strongly on the structural quality in a very peculiar way, since it increases when the structural defects are removed. It also varies strongly with the nominal composition of the sample increasing by a factor of almost 2.5 for only a 0.5% change in the composition. On the contrary, it is remarkable that the temperature dependence of the conductivity is almost independent of the composition and the structural quality. It is shown that, at low temperature, the temperature - and the magnetic field - dependence of the conductivity can be analyzed with classical weak localization theories including, however, strong electron-electron interaction similarly to that observed in systems close to a MIT. Similar peculiar behaviours are observed by preliminary measurements in the new AIPdMn stable icosahedral phase.