To form a high melting point intermetallic compound in the part requiring reinforcement, related to the cyinder of a engine, especially tot he cyinder head, at a low cost while saving energy.

A grooved part 14 is formed in respective narrow regions between an air intake 6 and an exhaust port 8 of a cylinder head and a secondary combustion chamber. A green compact 16, prepared by mixing a powdered metal consisting of a metal constituting the cylinder head and a powdered additive metal causing combustive synthetic reaction with the above metal in a prescribed ratio, is disposed in the grooved part 14. Subsequently, TIG arc heating is applied to the green compact 16 to ignite and burn it, by which the intermetallic compound is formed.