Seperate head texture from Body when export

Hi guys! I want to export a model from CC5 and want to combined UV of the body into 2 materials for a game model which is 1. Head material and 2. The rest of the body material. The reason for this is because I want the head material to be more detailed.
I tried to use combined UV for game character or by any type but it always combined the head with the body. Another way I found is to Export Head for Metahuman, The result of UV is very satisfying to me, but it only exported the head mesh.
If anyone can help me with this problem please tell me. Thank you in advance!