An intermetallic compound, La5Co19 is synthesized successfully for hydrogen storage, and its crystal structure is determined by X-ray diffraction. The alloy is formed by annealing the precursor at 1073 K for 10 h, and it has a La5Co19-type structure (space group R-3m, 3R) with a = 0.5130(1) nm and c = 4.882(1) nm. Its maximum hydrogen capacity reaches 0.92 H/M, but 0.40 H/M of hydrogen remains in the sample after the first desorption. Its reversible hydrogen capacity is 0.51 H/M. The formed hydride phases, phase I (La5Co19H10) and phase II (La5Co19H22) also have the La5Co19-type crystal structure; the hydride phases retain the same metal sublattice as that of the original alloy. Phase I is formed through anisotropic expansion of the La5Co19 lattice, while the unit cell, the MgZn2-type and CaCu5-type cells, of phase II is formed by the isotropic expansion of the La(5)Co(19)lattice. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.