[en] Complete text of publication follows: The purpose of the current work was to synthesize and investigate the hydrogen storage properties of ternary alloys from RE-M-Mg systems (RE-rare earth metals, M - transition element such as Ni and Cu). Alloys based on magnesium are known to store high amount of hydrogen (up to 7.7 wt.%) reversibly. Mg₂Ni-based alloys offer also very high capacity (up to 4 wt.% H₂). This storage capacity coupled with a low price and reversibility suggests that magnesium and magnesium-based alloys could be advantageous for use in battery electrodes and gaseous - hydrogen storage systems. Therefore, Mg-based and Mg₂Ni-based materials were in the focus of our studies. The REMg₂Cu₉ ternary compounds (where RE - Y, La-Nd, Sm-Ho, Yb) [1] and REMg₂(CuNi)₉ alloys (where RE = La, Tb, Pr) were synthesised. Crystal structure determination and microstructural characterisation were performed. LaMg₂Cu₉, TbMg₂Cu₉, PrMg₂Cu₉, LaNi₅Cu₄Mg₂ and TbNi₃Cu₆Mg₂ were chosen for the investigation of hydrogen storage properties. TbMg₂Cu₉ and PrMg₂Cu₉ did not absorb hydrogen in pressure range 1 to 10 bar and at the ambient temperature. LaMg₂Cu₉ absorbs 3 H/f.u (1.004 wt%) under 100 bar and at 25 C. LaMg₂Cu₄Ni₅ absorbs 1.6 H/f.u (1.002 wt%) under 10 bar and at 25 C. Pressure - hydrogen concentration isotherm was measured. TbMg₂Ni₃Cu₆ absorbs 3 H/f.u (1.004 wt%) under 100 bar and at 25 C. All the samples needed to be activated by heat treatment under vacuum followed by several absorption - desorption cycles