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We discuss recent high-field specific-heat measurements on the spin-Peierls compound tetrathiafulvalinium bis-cis-(1,2-perfluoromethylethylene-1-2-dithiolato)gold [TTF-BDT(Au)]. An ordering anomaly can clearly be detected which defines a high-field phase boundary, despite some extraneous structure in the data apparently reflecting experimental limitations. The high-field phase boundary is in good quantitative agreement with the theory of Cross and Fisher. Further, the specific-heat data are in good agreement with earlier ac susceptibility data, the reliability of which as indicators of a phase transition has been somewhat open to doubt because pronounced relaxation effects in the high-field regime result in striking differences between χac and χdc. Some observations are made concerning the extent of hysteresis associated with the phase boundary between dimerized and high-field phases. Finally, the extensive experimental data are employed in several tests to determine the applicability of recent soliton theories.

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©1987 The American Physical Society