Commensurate-incommensurate magnetic phase transitions in PrCu2Ge2and NdFe2Ge2

New neutron diffraction and ac magnetic susceptibility data concerning phase transitions and magnetic structures of PrCu2Ge2 and NdFe2Ge2 are presented here. In the case of PrCu2Ge2 at low temperatures collinear antiferromagnetic ordering of the AFI type is observed. In the temperature range between T-t = 5.5 K and T-N = 15.0 K the collinear and a sine wave modulated structure coexist. The latter phase is a long period modulation along the a-axis described by the propagation vector k (0.0336(5), 0, 0). In the case of NdFe2Ge2 the situation is similar: a collinear AFII-type low temperature phase (k = (0 0, 1/2)) changes into a non-collinear one (k = (0, 0, 0.46(1))) at about 12 K. In both compounds in all phases magnetic moments localized on rare earth ions are parallel to the c-axes.