What is Cu4C?

Answer 1

It would be called cupric carbide but it doesn't exist. Copper carbide, CuC is the only compound containg only copper and carbon.

Answer 2

Cu4C refers to copper(I) carbide, which is a chemical compound containing copper and carbon. It is a rare compound that forms under high pressure and temperature conditions. Copper(I) carbide is typically not stable under normal atmospheric conditions and can decompose.