Memory leak when changing material

Was having a weird memory leak that I could no pinpoint. After frying some neurons I found that when doing this:

 object.GetComponentInChildren(SpriteRenderer).material = object.GetComponent(Objects).object.normalMaterial;

unity simply adds another material to memory. Moreover, I would expect that some GC action would happen in the long run but no...

Anyone care to explain how to bypass this when I need to change materials in realtime without unnecessarily increasing memory usage?

Thanks