Structural, magnetic and electronic properties of hydrides synthesized under high hydrogen pressure were determined and discussed.

In contrast to very unstable ZrNi₅H_x or ZrCo₂H_x hydrides the ZrFe₂H_3.5 is metastable due to surface poisoning. At high pressure ZrFe₂H_3.5 irreversibly changes its structure.

Group of RFe₂ and RFeMn alloys can absorb 5H atoms p.f.u. forming stable hydrides of respectively orthorhombic and cubic structure.

The Laves RMn₂ alloys form interstitial hydrides RMn₂H_x (x ⿤ 5) which can transform into RMn₂H₆ covalent hydrides independently of the parent structure (C14 or C15) and R:Mn atomic ratio.

RMn₂H₆ hydrides have high resistivity with semiconductor-like behavior. This is opposite to R₇Rh₃ which are semimetals while their hydrides have metallic character.