A generalization of the Blume-Emery-Griffiths model is introduced in which an entropy stabilization of the high-temperature phase is controlled by a degeneracy parameter pу1. The model describes a first-and a second-order phase transition as a function of temperature between two ordered phases. This is relevant for the martensitic transition problem. Mean-field calculations and Monte Carlo simulations are presented. The model predicts a constant entropy change at the transition for various

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... ition temperatures in agreement with the behavior found experimentally.