ELECTRONIC-PROPERTIES OF STABLE QUASI-CRYSTALS - TOWARDS A SEMICONDUCTING QUASI-CRYSTAL

Anomalous transport properties are presented of a series of pure AlCuF e icosahedral phases of very high structural quality including a milli metre size single grain. The most salient feature is that all these me tallic samples present very high resistivity values close to the metal -insulator transition (MIT) using up to 10000 muOMEGA cm at 4 K in Al6 2.5Cu25Fe12.5. The resistivity at 4 K depends strongly on the structur al quality in a very peculiar way, since it increases when the structu ral defects are removed. It also varies strongly with the nominal comp osition 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 lo w temperature, the temperature - and the magnetic field - dependence o f the conductivity can be analyzed with classical weak localization th eories including, however, strong electron-electron interaction simila rly to that observed in systems close to a MIT. Similar peculiar behav iours are observed by preliminary measurements in the new AlPdMn stabl e icosahedral phase.