The analysis of high resolution synchrotron X-ray powder diffraction data of HMTTEF.C-60 (HMTTEF = hexamethylenetetratellurafulvalene) gave a triclinic unit cell with a 9.9297 Angstrom, b = 9.9359 Angstrom, c = 13.1472 Angstrom, a = 106.966 degrees, beta = 95.887 degrees and gamma = 118.252 degrees in the space group PT. Steric considerations suggest that there is a nearly close-packed layer of C-60 molecules in the ab plane, and HMTTEF molecules are sandwiched between layers of C-60. The compound is insulating and weakly paramagnetic and the charge-transfer is small.