ANOMALOUS ELECTRON-TRANSPORT BEHAVIOR IN THE ALPHA-ALMNSI APPROXIMANT CRYSTAL - IMPLICATIONS FOR PERFECT ICOSAHEDRAL CRYSTALS

Semi-metallic and unusual transport properties similar to those previously seen in the ordered i-phases are observed in the (1/1) crystalline approximant, also known as alpha-AlMnSi, of the i-AlMnSi system. By examining the electronic properties of the alpha-phase and other related phases of perfect icosahedral (i-) crystals, one can better understand the origins of the anomalous behavior observed. It is shown that the unique band structure effects caused by the icosahedral point group symmetry in the i-phases are responsible for the unusual electronic properties as well as the tendency toward electron localization seen in this new class of semi-metallic materials. The suppression of the anomalous electronic behavior in the amorphous phases and disordered i-phases gives further evidence of the presence of these band structure effects.