Set different uv map

I have a model with two uv maps created, the first one should be used for color normal and specular while the second one used for alpha map, I can’t figure out how to set the different uv maps. I read that from three 0.152 up to 4 uv maps are supported but I don’t know how to tell the material field of the alpha map to use the other uv. Thanks a lot for the help may be what you’re looking for :eyes: