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Contains fulltext : 145259.pdf (Publisher’s version ) (Open Access) 5 p.

Polygrain icosahedral i-Al-Pd-Re quasicrystals are known to exhibit dramatically different electronic transport properties to other Al-based quasicrystals. By performing comparative experimental and theoretical studies of the electronic transport and electronic structure of polygrain and monocrystalline i-Al-Pd-Re samples, we show that the extraordinarily high electrical resistivity and the metal-to-insulator transition in the polygrain material are not intrinsic properties of the quasiperiodic lattice, but are of extrinsic origin due to the high porosity and the oxygen-rich weakly insulating regions in the material. We also compare theoretical electronic structures and experimental electrical resistivities of monocrystalline i-Al-Pd-Re and i-Al-Pd-Mn quasicrystals and show that there are no significant differences between these two isomorphous compounds, suggesting that i-Al-Pd-Re is on common ground with other Al-based quasicrystals. We present a structural model of i-Al-Pd-Re.

We report measurements of the normal state magnetoresistance (MR) from 30 to 340 K in fields B up to 13 T for single crystals of overdoped Tl2Ba2CuO6 (T-c less than or equal to 25 K). For out-of-plane current flow, the transverse MR Delta rho(c)/rho(c) is large and positive. On rotating B within the a-b plane, Delta rho(c)/rho(c) exhibits a striking anisotropy with fourfold symmetry. The amplitude of this effect increases as B-4 and the maximum MR occurs for B along the [110] crystallographic directions, i.e., at 45 degrees to the Cu-O-Cu bonds. This the first direct evidence for anisotropy of the in-plane mean free path in the cuprates.