Abstract
Al-based icosahedral quasicrystals and their corresponding approximants are characterized by large electrical resistivity, large thermoelectric power, and very small thermal conductivity. The factors leading to these characteristics were investigated by use of their crystalline approximants, which allow us to employ the structure analysis, band calculation, and phonon calculation well developed for crystalline materials. It is found that the quasiperiodic order does not play an exclusive role in providing the characteristic thermoelectric properties, while the icosahedral-symmetry and the characteristic quasi-Bllirouin-zone significantly contribute to these properties by deepening pseudogap at the Fermi level, reducing the mumber of acoustic phonons, and enhancing Umklapp scattering of phonons.
