Abstract Single crystals of CsAlF4 have been prepared from a mixture of CsF and AlF3 and investigated by X-ray methods, CsAlF4 crystallizes hexagonally (isostructurally to the new CsCrF4-type) with a = 9.500, c= 3.713 Å, Z= 3, space group P62m-D3h3, No. 189. AgAlF4 crystallizes orthorhombically (isostructurally to a-RbFeF4) with a = 7.108, b = 7.111, c = 5,568 Å, Z = 4.

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Single crystals of AgGdF4 have been investigated by X-ray methods. AgGdF4 is hexagonal (isostructural to NaNdF4) with a = 6.233, c = 3.599 Å, Z, = 3/2. Guinierphotographs give the same structure for AgLnF4-compounds with Ln = Nd, Sm-Ho. The other five (Ln = Er-Lu, Y) crystallize trigonal (isostructural to KErF4) in a superstructure variant of the CaF2-type (Z = 18).

Unit cell dimensions of new Ag3MF6 com­pounds have been determined by Guinier-photographs: Ag3AlF6 and Ag3GaF6 crystallize tetragonally (isostructurally to Rb3TlFe); Ag3ScF6, Ag3lnFe and Ag3TlF6 are monoclinic (Na3AlF6- type). AgGaF4 crystallizes tetragonally (iso­structurally to KFeF4), AgScF4 monoclinic in a new, unknown structure type.