[Closed] Save Mtl to sceneMtl?

This should be trivial…

		 MtlBaseLib* currentmatlib  =  GetCOREInterface()->GetSceneMtls();
		 currentmatlib->AddMtl(myMtl,TRUE);

But that material is not added even if when I save the scene I call:

		 currentmatlib->Save(isave);

When I re-open the scene that material is still on my medit (I’ve taken it from there) but not in the scene used mats.

Any clue on this? Thanks in advance.