  X-ray diffraction experiments were performed on polycrystalline and
single-crystal specimens of Ce$_{2}$Fe$_{17}$ at temperatures between 10 K and
300 K. Below $T_{\mathrm{t}}$ = 118$\pm$2 K, additional weak superstructure
reflections were observed in the antiferromagnetically ordered state. The
superstructure can be described by a doubling of the chemical unit cell along
the $\mathbf{c}$ direction in hexagonal notation with the same space group $R
\bar{3} m$ as the room-temperature structure. The additional antiferromagnetic
satellite reflections observed in earlier neutron diffraction experiments can
be conclusively related to the appearance of this superstructure.
