The data presented in this article is the supplementary data of Zhang et al. (2018) [1]. The Ni50Mn38Sb9Si3 alloy is annealed at 1223 K for 24 h and then quenched into ice water; while the Ni50Mn38Sb9.5Si2.5 alloy is annealed at 1173 K for 24 h and then quenched into ice water. The microstructure of the Ni50Mn38Sb9Si3 alloy indicates that a higher heat treatment temperature cannot prevent the formation of secondary phases. Furthermore, the composition of α phase is similar to the nominal composition of the alloy. On the other hand, the nominal concentration of Si atoms and heat-treatment temperature do not affect the compositions of the β and γ phases. For example, the compositions of the β and γ phases in the Ni50Mn38Sb9Si3 alloy are similar when annealed at 1223 K for 24 h and 1173 K for 24 h.