Heterometallic coordination polymers have attracted attention due to their varied topologies and potential of practical applications to the development and production of ceramic materials with interesting physical properties such as superconductivity, colossal magnetorezistance, or phase separation [1]. In continuation of our studies [2], we report here synthesis and structural characterization of MnII-Ba heterometallic coordination polymer based on 2,3-pyridinedicarboxylic acid (H2L), {[MnBaL2(H2O)5]·3H2O}n (1) and SQUID at 2-300K. Crystallographic studies revealed that 1 crystallizes in a triclinic system, space group P-1, a = 8.9634(5) Å, b =11.3646(8) Å, c =11.6001(6) Å, α=101.639(5)°, β=92.050(5)°,γ=106.057(6)°. The octahedral coordination surrounding of MnII atom is completed by two symmetry independent organic ligands coordinated in chelate N,O-fashion, water molecule and oxygen atom of one symmetry related complex. The organic ligands bear different structural functions. One of them is pentadentate, double bridges the MnII atoms in dimeric [Mn2L4(H2O)2] unit, and additionally coordinates to BaII atoms in monodentate and µ2-bridging fashion through the peripheral carboxylic oxygens. The other ligand is tridentate and coordinates to BaII atoms only in monodentate manner. Thus, the ligands unite MnII and BaII metals in dimers and dimers in 2D layer, fig.1. The BaII sites are decacoordinate due to coordination of terminal and bridging water molecules, the later join Ba in the chain along a crystallographic axis with Ba...Ba separation 4.207 and 5.249Å the layers in 3D network. The susceptibility data of (1) (fig.2) indicate the existence of MnII centres in a high-spin state (S = 5/2). No noticeable magnetic exchange interactions were observed between the Mn(II) ions, which behave paramagnetically in the temperature range 2 – 300 K. However, for the precise description of the experimental magnetic data at low temperatures (T < ~10 K) the tiny influences of a ground state zero field splitting effect (D = 0.62 cm-1, gz = 1.98, gxy = 2.03) and intermolecular interactions (zJ’~-0.18 cm-1) should be included.