The search for ferromagnetic semiconductors and stable half-metallic ferromagnets remains a high priority in solid-state physics. A general understanding of structureproperty relationships is a necessary prerequisite for the design of new materials. In this study, the band structures and magnetic properties of the form XCaZ (Y = Ca) compounds in the half-Heusler structure have been calculated with the full-potential linear augmented plane wave (FP-LAPW) method within the spin density functional theory. The calculations reveal that the nonmagnetic element can induce stable ferromagnetic state in alkaline metals. The most stable atomic arrangement is when XCaZ occupy the (0, 0, 0), (1/4, 1/4, 1/4) and (3/4, 3/4, 3/4) positions. For the majority spin channel the Fermi level is located in the band gap, and for the minority spin there is no energy gap around the Fermi level, which gives a direct evidence of the half-metallic behavior.