Slow diffusion of two aqueous solutions containing K(4)[Mo(CN)(7)].2H(2)O and [Mn(H(2)O)(6)](NO(3))(2), respectively, has afforded two kinds of single crystals whose formulas are Mn(2)(H(2)O)(5)Mo(CN)(7)].4H(2)O (alpha phase) and Mn(2)(H(2)O)(5)Mo(CN)(7)].4.75H(2)O (beta phase). This paper is devoted to the latter compound. It crystallizes in the monoclinic system, space group P2(1)/c, a = 7.885(3) Å, b = 10.406(7) Å, c = 25.233(11) Å, beta = 98.11(2) degrees, Z = 4. The Mo site is surrounded by seven -C-N-Mn linkages in a distorted pentagonal bipyramid fashion. There are two distorted octahedral Mn sites, one with four and the other with three -N-C-Mo linkages. The structure is three-dimensional. It consists of bent ladders made of edge-sharing (MoCNMnNC)(2) lozenge motifs running along the a direction. These ladders are linked further along the a and c directions. The a, b, and c axes were determined to be the magnetic axes. Both temperature and field dependence of the magnetization have been measured along the magnetic axes. The angular dependence of the magnetization in the ab plane as a function of the external field has also been measured. Single crystal magnetic measurements revealed that the compound orders ferromagnetically at T(c) = 51 K, without a hysteresis effect. They have also shown that the compound has a complex magnetic phase diagram when the field is applied along the a direction, with several ferromagnetically ordered domains and a spin reorientation domain. The boundaries between these domains have been determined. These results have been compared to those obtained with Mn(2)(H(2)O)(5)Mo(CN)(7)].4H(2)O (alpha phase).