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The crystal structure of non-metamict Ti- and Fe2+-rich chevkinite-(Ce) has been redetermined with the single-crystal sample colleeted from Bayan Obo, Inner Mongolia,China The chemical formula of the sample is Ce4Fe2Ti3Si4O22. The crystals are monoclinic with the unit cell parameters a= 13.4656(15) A;b=5:7356(6)A,c =11.0977(12) A, β= 100 636(2)° V = 842.39 (16) A3 and Z =2.The structures of Ti- and Fe2+-rich chevkinite-(Ce)were refined with space groups P2/a and C2/m. Least-squares refirement results show that both structural models of Ti- and Fe2+- rich chevkinite-(Ce) are very good, R[F2＞2σ(F2)] =0.027 with P21/a and R[F2＞2σ(F2)] =0.021 with C2/m In order to illustrate the relationship between the two space groups P21/a and C2/m,the distribution of diffraction intensities was inspected. Pseudo extinction was found,i.e., reflections with h+k=2n are systematically strong,while those with h+k=2n+ 1 are weak. By neglecting the systematically weak (h+k=2n+1)reflections the space groupbecomesC2/m.There is a mirror plane in the C2/m perpendicular to the b axis However, oxygen atoms in the P21/a model are of a symmetrical relationship with the corresponding pseudo mirror plane It is concluded that the crystal structure of non metamict Ti-and Fe2+-rich chevkinite-(Ce) is a superstructure with the space group of P21/a, which is of pseudo symmetrv coprresponding to the space group C2/m.