Lanthanum forms several alloys with nickel, including LaNi<sub>5</sub>, La<sub>2</sub>Ni<sub>7</sub>, LaNi<sub>2</sub>, LaNi<sub>3</sub>, La<sub>2</sub>Ni<sub>3</sub>, LaNi and La<sub>3</sub>Ni etc.
LaNi<sub>5</sub> is an intermetallic compound with a CaCu<sub>5</sub> structure. It belongs to the hexagonal crystal system. It can be oxidized by air above 200 ðC, and react with hydrochloric acid, sulfuric acid or nitric acid above 20 ðC. LaNi<sub>5</sub> can be used as a catalyst for hydrogenation reactions.
In addition to LaNi<sub>5</sub>, there are other alloys such as La<sub>2</sub>Ni<sub>7</sub>, LaNi<sub>2</sub>, LaNi<sub>3</sub>, La<sub>2</sub>Ni<sub>3</sub>, LaNi, and La<sub>3</sub>Ni, and nonstoichiometric alloys such as LaNi<sub>2.286</sub> (tetragonal, space group I4ÃÂ2m). The nickel atoms in La<sub>x</sub>Ni<sub>y</sub> can also be replaced by other atoms, such as LaNi<sub>2.5</sub>Co<sub>2.5</sub>.