[en] We report the synthesis of the first salt of the organic donor, bis-(ethylenedithio)tetrathiafulvalene (BEDT-TTF or simply ET), with a square-planar anion, AuCl₄/sup /minus//, which leads to the 2:1 salt β-(ET)₂AuCl₄. The crystal structure analysis shows that the two-dimensional ET molecular network is comparable to that found in the ambient pressure superconductors β-(ET)₂X (X/sup /minus// = I₃/sup /minus//, IBr₂/sup /minus//, and AuI₂/sup /minus//), with similar short interstack S/hor ellipsis/S contacts of /approximately/3.60 /angstrom/. During our attempt to obtain low temperature x-ray diffraction data we discovered a destructive phase transition upon prolongated cooling to 130 K. The transition originates from extremely short hydrogen/hor ellipsis/halogen contacts that occur when the conformation of an ethylene group of ET is frozen as the temperature is lowered. 21 refs., 5 figs., 5 tabs