Magnetoresistance of an insulating quasicrystalline AlPdRe film in large magnetic fields

A metal-insulator transition in a quasicrystalline icosahedral AlPdRe film series was recently observed. The resistance of one of the films follows an activated Mott variable-range hopping law, thus indicating insulating behaviour. The magnetoresistance (MR) ratios r = R(B, T)/R(O, T) of this insulating film exhibited large positive values at low temperatures of 93 mK and magnetic fields up to 17 T. The data are fitted using the wave function shrinkage model for insulating films, and the fits to the data above 1 K are acceptable. The low temperature MR data exhibit anomalous behaviour at high fields above 12 T, characterized by a saturation of the ratio data and followed by a turnover to smaller values. A possible explanation for the saturation of the R(B, T)/R(O, T) ratio is proposed involving a field dependence of the localization length and of the density of states, which both appear in the wave function shrinkage theory. In contrast, the weak localization theory and electron-electron interaction theory, used to describe electronic transport in metallic films, failed badly to describe the transport data of this insulating film.