Hi
I am using ent_createlayer(...)

so the created entity is affected by the sun_light and sun_position, I want to prevent that from happening.
also I want them to have a material using mtl_create()

You may have a look at albedo in the manual.

MATERIAL* mtl_nosun = {
ambient_blue = 100;
ambient_green = 100;
ambient_red = 100;
albedo = -100;
}