To obtain a new compound effective for forming a silver halide color photosensitive material having slight fog, excellent sensitivity, graininess and improved shelf stability by using a specific organometallic compound.

This compound is an additive for photography and is shown by formula I [Y1 is As or Sb; X1 is S, Se or Te; R1 is a group of the formula N(R5)R6 (R5 and R6 are each an aliphatic group, an aromatic carbon ring group, a heterocyclic group or H), R5, a halogen, a group of the formula OR4 (R4 is R5 or a cation), a group of the formula SR7 (R7 is R4), a group of the formula OSi(R8)(R9)R10 (R8 to R10 are each an aliphatic group) or the like] such as tri-t-butylarsenic selenide of formula II. The compound of formula II is obtained by heating tri-t-butylarsenic of formula III with metal selenium in tetrahydrofuran under reflux. Preferably, in the case of using the additive for forming a silver halide color photographic sensitized substance, the amount of the additive used is 10-8 to 10-2 mol based on 1 mol of silver halide.