Anomalous Electron Transport Behavior in the α-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 α-AlMnSi, of the i -AlMnSi system. By examining the electronic properties of the α-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.