The three selected compositions MgTiVZrNbHf, MgAlTiVCr and MgTiCrNb were successfully prepared by a two-step method mainly due to the Mg high vapour pressure that hinders the use of high temperature melting technique. The RBM technique under high H 2 pressure permits direct production of hydride phases of these compositions with high hydrogen content: 1.6, 1.34 and 1.85 H/M for MgTiVZrNbHf, MgAlTiVCr and MgTiVCrNb, respectively. The crystalline lattice of the obtained hydrides phases is FCC (F m 3m) as shown in Figure , typical for full hydrides of BCC high entropy alloys. The lattice parameters of the FCC hydrides are 4.612(2) Å, 4.297(2) Å, and 4.464(5) Å for MgTiVZrNbHf, MgAlTiVCr and Mg-TiVCrNb, respectively. A small amount of secondary amorphous phase (possibly poorly crystalline BCC phase) can be noticed at 2θ around 40 o for the composition MgAlTiVCr. This might explain the lowest hydrogen capacity of this phase relative to the other compositions and be consistent with slight and small Al enrichment zones observed by EDS (Figure ). It is worth mentioning that hydrogen can be desorbed from these initial hydrides by heating up to 450 o C under secondary vacuum and the desorbed phases adopt a BCC lattice (Im 3m), as expected for these materials (see TDS measurements and XRD patterns of the BCC phases after desorption in the SI).