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Magnets with chiral crystal structures and Dzyaloshinskii-Moriya (DM) interactions have recently attracted much attention as potential spin-electronics materials [1]. Mn-based intermetallic compounds have gained particular interest, because they often favor noncoplanar spin structures including skyrmions [2, 3], and their magnetic and electron-transport properties are also tunable by alloying and varying Mn content [3]. In this work, Mn_5+xSi_2-x alloys (x = 0, 0.1, and 0.2) were prepared using arc-melting process followed by annealing at 800 °C for 12 hours. Rietveld refinement analysis on x-ray diffraction data shows that the Mn₅Si₂ compounds form tetragonal structure with a = 8.914 Å and c = 8.719 Å and a space group P4₁2₁2, which can support spin spirals caused by DM interactions. The effect of Mn/Si ratio on the magnetic properties will be discussed.