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 A l(70.5)Pd(21)Res(8.5), and With resistance ratios R [=rho(4 K)/rho(295 K)] from 2 to 120, has been measured in the range 0.1-40 K in magnetic fields u p to 12 T. Three regions of the MR can be distinguished. For R up to 13 qua ntum interference effects (QIE) describe the observations well. MR in exces s 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 l owest temperature, 0.2 K, and increases in magnitude with R. From analyses within QIE the Coulomb interaction parameter above R approximate to 10 and the inelastic-scattering time decrease with R, and the results indicate tha t this may be the case also for the spin-orbit-scattering rate. For R great er than or equal to 50, weak localization has broken down. Samples prepared by two different methods were studied in this region of R. Although the te mperature dependence of the electrical resistivity and the MR at temperatur es above 4 K are similar for similar R values in both sets of samples, sign ificant differences were observed;below 1 K. We discuss this MR in the ligh t of current theories on both sides of an MIT and conclude that none of the se theories can fully reproduce the observed features for samples in this r ange.