Magnetoresistance of icosahedral Al-Pd-Re: From weak localization through breakdown to a high-resistivity regime

The magnetoresistance (MR) of icosahedral Al-Pd-Re of nominal composition Al70.5Pd₂₁Re8.5, and with resistance ratios R [={ρ}(4 K)/{ρ}(295 K)] from 2 to 120, has been measured in the range 0.1--40 K in magnetic fields up to 12 T. Three regions of the MR can be distinguished. For R up to 13 quantum interference effects (QIE) describe the observations well. MR in excess of 100% was observed at low temperatures in this region. For R increasing above 13, the approach of a possible metal-insulator transition (MIT) can be followed in the results. A new negative MR contribution emerges at the lowest temperature, 0.2 K, and increases in magnitude with R. From analyses within QIE the Coulomb interaction parameter above R≈10 and the inelastic-scattering time decrease with R, and the results indicate that this may be the case also for the spin-orbit-scattering rate. For $R>~50,$ weak localization has broken down. Samples prepared by two different methods were studied in this region of R. Although the temperature dependence of the electrical resistivity and the MR at temperatures above 4 K are similar for similar R values in both sets of samples, significant differences were observed below 1 K. We discuss this MR in the light of current theories on both sides of an MIT and conclude that none of these theories can fully reproduce the observed features for samples in this range.