Investigation of half-metallicity in the rare-earth-based new Heusler alloy has been performed. Three different crystal structures are studied, corresponding to different basis arrangements in the lattice in addition to magnetic and non-magnetic configurations. A study of electronic energy band structures is carried out to reveal the nature of the sample alloy. Because of the presence of d and f orbitals, the Hubbard correction term (U) is calculated and incorporated in the calculations. Computation of magnetic moments reveals the magnetic behaviour of the sample alloys, and the origin of the magnetism is realised by analysing the bands. The study predicts magnetic semi-conductor type of Half-metallic behaviour with ferromagnetic configuration in the sample Heusler alloy, making it a potential candidate material for various spintronic applications.