A new phase in the samarium-germanium system has been shown by X-ray diffraction techniques to have the stoichiometry SmsGe4. The crystals are orthorhombic with a=7.75, b= 14.94, c=7.84/~; Dr = 7.62 g.cm-3 for four SmsGe4 units per unit cell. Systematic extinctions are characteristic of the space groups Pnma and Pn21a. The structure is conveniently described in terms of three layers which occur along the b axis. Layer G contains Ge atoms only; layer S, Sm only. Layer C is a combination of G and S, but with the roles of Ge and Sm interchanged. Layer C serves as a mirror plane in Pnma, but only as a quasi-mirror plane in Pn21a. Least-squares refinement in Prima gives an R index of 9.3 %; in Pn21a, an R index of 9.0 %. Differences between the two sets of parameters are small, and it is concluded that the structure is adequately described in terms of Pnma. The similarity of the layers to those occurring in CuA12 and U3Si2 is noted.
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