Conductivity of icosahedral Al-Pd-Re at ultralow temperatures

The low-temperature electrical conductivity sigma(T) has been studied for f our samples of icosahedral Al70.5Pd21.0Re8.5 in the form of annealed ingots . The resistance ratios R = rho(4 K)/rho(295 K) were in the range 70-180. T he overall temperature dependence of the conductivity below 1 K is stronger than for previously reported results and the conductivity is lower. Two sa mples were measured down to 15 mK and two down to 0.1 mK. For the latter sa mples sigma(T) attained constant finite values at the lowest temperatures. A variable-range-hopping mechanism is discussed. It is concluded that the c onjecture for a metal-insulator transition in i-AlPdRe remains unresolved a nd that measurements must include temperatures below 15 mK on samples of hi gher residual resistance ratios to settle this problem. [S0163-1829(99)0803 9-X].