Several compositions of the type Sr xYb 1-xF 3-x (x = 0.20, 0.25, 0.30. 0.33) were prepared by heating the well ground mixtures of appropriate amounts of SrF 2 and YbF 3 at 1100°C. The substitution of Yb 3+ in YbF 3 by Sr 2+ for x = 0.25 and 0.3 leads to new single phasic fluorides with tysonite type structure. Quenching was shown to be essential to stabilize these phases. The XRD pattern of Sr 0.25Yb 0.75F 2.75, i.e., SrYb 3F 11 was fitted on a hexagonal unit cell with space group P6 3/mmc with a = 3.9606(4) and c = 6.9731(5) Å. According to Rietveld refinements the as prepared SrYb 3F 11 crystallizes in the disordered HT-form of the tysonite type structure. The magnetic measurements of Sr 0.25Yb 0.75F 2.75 show paramagnetic behaviour with a magnetic moment of 4.6 μ B which corresponds to the f 13 configuration of Yb 3+.