Co, Fe, Mn) alloys were synthesized by the sintering method and characterized by X-ray powder diffraction method. All phases belong to the SnMgCu 4 structural type (space group F-43m). Rare earth metal atoms occupy the position of Mg atoms (4a), Mg atoms are located in the Sn sites (4c), and transition metal atoms distribute the Cu positions (16e). Three selected alloys were hydrogenated. The alloys easily absorb hydrogen at room temperature and maximum pressure up to 10 bar. One orthorhombic YMgNi 3 FeH 4.2 (structural type NdMgNi 4 D 3.6 , spatial group Pmn2 1 ) and two cubic YMgNi 2 Fe 2 H 5.0 and YMgCo 2 Cu 2 H 3.8 (structural type LaMgNi 4 D 4.85 , spatial group F-43m) were synthesized. Volume expansion of the unit cell for saturated hydrides compared to their parent alloys is in the range 12-14%. In general, volume evolution is in good agreement with absorbed quantity of hydrogen.Electrode materials for the selected alloys were made and their main electrochemical characteristics (maximum discharge capacity and cyclic stability) were established. The nature of the transition metal is crucial in yttrium alloys. RMgM 4 alloys containing only Co, Fe, Cu are characterized by very low values of the discharge capacity, which does not exceed 50 mAh/h. YMgNi 4 -based alloys have elevated discharge capacity. Replacing nickel in the YMgNi 4 alloys by iron or manganese leads to some increase and then decrease discharge capacity. It is highest in the YMgNi 3 Mn (287 mAh/h) and YMgNi 3.5 Fe 0.5 (178 mAh/h) electrodes. When CeMgCo 4 is replaced by nickel the value of discharge capacity decreases. It is high only in alloys with the highest cobalt content: CeMgNiCo 3 (C max = 104 mAh/h).