Neutron-diffraction evidence for ordering in the high-$T_c$ phase of $\beta$-di [bis (ethylenedithio) tetrathiafulvalene] triiodide [${\beta }^{*}-{\left(\mathrm{ET}\right)}_2{\mathrm{I}}_3$]

Satellite reflections, which are present in the neutron-diffraction pattern of $\beta$-di [bis (ethylenedithio) tetrathiafulvalene]triiodide [$\beta -{\left(\mathrm{ET}\right)}_2{\mathrm{I}}_3$] at ambient pressure below 200 K, are absent above a critical pressure of 0.5 kbar applied at room temperature and followed by cooling. The satellite reflections remain absent if the pressure is released while the temperature is maintained at 20 K. The absence of satellite reflections, and therefore the absence of a previously discovered modulated structure, indicates a higher degree of ordering in the high-pressure-high-$T_c$ state in comparison to the ambient-pressure-low-$T_c$ state of $\beta -{\left(\mathrm{ET}\right)}_2{\mathrm{I}}_3$.