[godelski]

Alloys, composites, raw materials, you can identify them. If they have atoms you can identify what is in them. Now there could be weird materials that are hard to more difficult to identify. But you need a more compelling argument.

Extraordinary claims require extraordinary evidence.

[joshuaheard]

If they have a vehicle whose flight defies our knowledge of physics, maybe it's made from a material that does the same.