Adding a small amount of solid carbon to copper boosts its conductivity

https://phys.org/news/2023-12-adding-small-amount-solid-carbon.html

"added 18 ppm graphene to electrical-grade copper, the temperature coefficient of resistance decreased 11% without decreasing electrical conductivity at room temperature. and 1% motor efficiency gain... solid-phase processing extrudes composite wire leading to uniform, near pore-free microstructure punctuated with tiny flakes and clusters (making better high-temperature conductors) of graphene responsible for decreasing coefficient of resistance... now measuring strength, fatigue, corrosion, and wear resistance"

Related: These Four Teams Are Building a Better Copper or Trying To Replace It
https://www.nrel.gov/news/program/2024/copper-is-king-but-its-time-for-a-metal-meritocracy.html