Electrical properties of approximant phases in Al–Pd–(Fe, Ru) systems

X-ray diffraction patterns of structurally ordered 1/0 cubic approximant phases in the Al–Pd–(Fe, Ru) ternary systems are presented. The 1/0 approximant in the Al–Pd–Fe system was found to possess a body-centered lattice with a=15.3 Å, whereas that in the Al–Pd–Ru system a face-centered one with a=15.5 Å, and the results were compared with the reported structural models. Their electrical resistivities have been investigated and found to be substantially high for the lowest order approximants: ρ300 K∼1000 μΩ cm. In addition, negative temperature coefficients accompanied by a distinctive resistivity maximum in the ρ–T curves have been observed. The peculiar ρ–T dependences will be described in terms of the quantum interference effects with strong spin–orbit scattering and it will be shown that the transport properties of 1/0 approximants are quite sensitive to disorder reflecting the flexibility of their structure.