Abstract

Abstract Electrical resistivity, magnetoresistance, and specific heat measurements have been performed for the binary icosahedral Cd 5.7 Yb and its cubic approximant Cd 6 Yb. The resistivity of both the icosahedral phase (i-phase) and the approximant is found to show a rather metallic behavior with a large positive temperature coefficient of the resistivity (TCR) below 200–300 K followed by leveling-off at low temperatures below 10 K. For the approximant, we observe a stepwise change of the resistivity at 110 K which is due to a phase transition. Giant magnetoresistance as high as 200% at 9 T below 4.2 K is observed for the i-phase and the electronic specific heat coefficient γ is found to be extraordinary large in both alloys, i.e., 2.87 mJ/(mole K 2 ) for the i-phase and 7.60 mJ/(mole K 2 ) for the approximant. Such large γ values may be attributed to the Yb-derived states at the Fermi level. Furthermore, the Debye temperatures ( Θ D ) are very low and almost the same for both alloys, i.e., 142 and 144 K, respectively, which are indeed the lowest values ever reported in i-phases and approximants. The metallic character of the binary i-phase implies that the negative TCR is not necessarily a consequence of the quasiperiodicity.

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