In the reaction of copper nitrate with barium salicylate in methanol at a constant stirring and room temperature and further recrystallization from the mixture of dimethylacetamide (DMAA) and tetrahydrofuran (THF) solvents, the complex with the composition [CuBa(SalH)4(DMAA)4(H2O)] was obtained as crystals of intense blue colour.  In EPR measurements, was used the single crystal with the sizes (0.8 x 0.9 x 1.8) mm3. For determining the main values of g- and a- tensors the selected single crystal was rotated in three planes XOY, YOZ and ZOX. Because of the orientation of principal axes of the crystal with respect to the magnetic field, the EPR spectrum has changed from a single resonance line (Fig. 1) to a four component spectrum (Fig. 2). It is due to the hyperfine interaction between unpaired 3d-electron of Cu2+ ion and copper nucleus with the spin I = 3/2, including both isotopes 63Cu and 65Cu with natural abundances 69.09 % and 30.91 %, respectively. Note that Cu2+ ions are part of the crystalline lattice. Therefore, for revealing a hyperfine structure in this case, a sufficiently large distance is necessary between Cu2+ ions that leads to the spectral resolution of a hyperfine structure. This is possible because there exist Cu2+-Ba2+ dimers, where Ba2+ is a diamagnetic ion.  Based on experimental data and by using the method described in [1], the following secular equation for finding the main values of g-tensor was obtained:  λ 3 – 13.9579 λ 2 + 64.5100 λ – 98.8077 = 0. (1)  The main values of the g-tensor are:  gzz = 2.324 ± 0.002, gxx = 2.092 ± 0.002, gyy = 2.044 ± 0.002. (2)  These values of the g-tensor are in agreement with the structural data. Analogically, the main values of the a-tensor have been determined based on the following secular equation:  Ɛ 3 – 2.8065 Ɛ 2 + 1.4213 Ɛ –0.0817 = 0. (3)  The main values of the a-tensor are:  azz = (14.73 ± 0.01) mT, axx = (7.57 ± 0.01) mT, ayy = (2.57 ± 0.01) mT. (4)  The obtained data for main values of g- and a- tensors are in agreement with analogical data for the [CuCa(SalH)4(DMAA)4(H2O)] single crystal (see another our abstract in this Abstracts Book).