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Tunnelling states have been found in a single grain of an Al-Pd-Mn quasi-crystal free of phason strain. Their density of states and their properties are quite similar to those in amorphous metals. These results are obtained from the study of the propagation of acoustic shear waves at high frequency (up to 430 MHz) and low temperature (down to 10 mK).
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Vernier et al. (1993) studied this question.
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