We report the first X-ray diffraction and Raman spectroscopy study of a single crystal of the rare-earth endohedral fullerene Dy@C . The lattice is found to be body-centered cubic (a = 25.79 Å, space group I4̄3d) which is at variance with previous reports and confirms that several types of structures can be stabilized in Dy@C . X-ray diffraction/diffuse scattering methods reveal no low-temperature change down to 12 K for the present structure. The Raman spectroscopy data are comparable to those of other M@C endohedral compounds. However, the Dy oxidation state and the force constant of the low-frequency metal-cage stretching mode do not follow the simple relationship observed before. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2003.