Ferromagnetic and structural properties of semimagnetic (diluted magnetic) monocrystalline Ge1-xMnxTe layers (x = 0.04 and x = 0.19) grown by molecular beam epitaxy on BaF2(111) substrates were experimentally studied by the SQUID magnetometry and by high resolution X-ray diffraction analysis. Based on the temperature dependence of the lattice parameter, the structural phase transition from the rock salt to the rhombohedral crystal lattice was experimentally found at T = 675 K in Ge1-xMnxTe (x = 0.04) layer. The ferromagnetic Curie temperature T-c in Ge1-xMnxTe layers was determined based on the measurements of temperature and magnetic field dependence of magnetization. In Ge1-xMnxTe with the highest Mn content studied (x = 0.19) the mean-field like analysis of magnetic properties showed the Curie temperature T-c = 40 K.