Composition dependence of the electronic properties of Al-Cu-Fe and Al-Cu-Ru-Si semimetallic quasicrystals

Electronic transport properties and specific heats of ordered icosahedral phase alloys in the Al-Cu-Ru-Si and Al-Cu-Fe systems are examined, and comparison with high-quality rhombohedral (3/2) approximant phase samples of Al-Cu-Fe is made. Strong temperature dependence and sensitivity to composition changes of these properties are observed. The similarity of transport properties between the icosahedral (i) and rhombohedral (r) phases of ${\mathrm{Al}}_{62.5}$ ${\mathrm{Cu}}_{26.5}$ ${\mathrm{Fe}}_{11}$ is noted. The results can be qualitatively interpreted in terms of band structure. There appears to be sufficient evidence for a rapidly varying conductivity spectrum σ(E) in the ordered i phases. However, important questions concerning the physics of these semimetallic quasicrystals remain to be answered.