Complex phosphates containing two different ions have been identified in the fluxes of M2O-P2O5-Mn2O3 systems (where M - Na, K) for the first time. Optimum conditions for the growing of single crystals of NaMn6(P3O10)(P2O7)2 and KMn6(P3O10)(P2O7)2 compounds have been selected. Complete X-ray diffraction analysis has been performed to study single crystals of synthesized phosphates MMn6(P3O10)(P2O7)2 (where M - Na, K). The structure of compounds is defined by the monoclinic crystal system (space group P21/m) with lattice parameters: a = 5.350 (5.358) A, b =26.643 (26.697) A, c = 6.566 (6.575) A, [beta] = 107.250 (107.220); Z = 2, [rho] = 3.575(3.568) g/cm3, respectively. The synthesized compounds have been studied using the following techniques: DTA, IR- and EPR-spectroscopy, magnetochemistry; the dependence of dielectric constant on the temperature has been measured for the obtained phosphates. Slight antiferromagnetic interaction has been detected in octahedron chains [MnO6]. Based on the findings from conducted research, a set of physicochemical properties has been proposed for the synthesized compounds, which can be utilized in the development of these functional materials.