[en] The structural, electronic, bonding, elastic and mechanical properties of osmium intermetallic OsX (X = Al and Si) compounds in B2-phase as well as in B20-phase have been studied using full-potential linearized augmented plane wave method in the framework of density functional theory within generalized gradient approximation. The calculated lattice constants (a0) and bulk modulus (B) are in good agreement with experimental and available theoretical results. From the band structure calculations, it is shown that OsAl is metallic in both the phases while OsSi is found to be semiconductor in B20-phase with the indirect band gap of 0.33 eV but at high pressure the density of states at Fermi level N(EF) decreases and the bands spread over the entire reason in both the compounds. The elastic constants of these compounds obey the stability criteria for cubic system at 0 pressure as well as at high pressure. With increasing pressure, all the elastic constants for OsAl and OsSi increase almost linearly with pressure in both the phases except C44 for OsAl-B20 which shows its softening nature. Bonding nature is discussed in terms of charge density difference plots and Fermi surfaces. (author)