New Phase Transition Observed at 46 K in Tetrathiafulvalene-Tetracyanoquinodimethane (TTF-TCNQ)

We have measured the heat capacity of TTF-TCNQ in the vicinity of the low-temperature transitions. High-resolution measurements, realized by the improvement of standard relaxation techniques, lead to the observation of four phase transitions at 52.6, ∼ 49-48, 46, and 37 K. The new transition observed at 46 K is tentatively attributed to the softening of $0.59b^{*}$ mode in TTF-TCNQ.