Compounds that have superconducting properties even in high magnetic fields and temperatures up to 77 Kelvin. They are a high-temperature superconductor and a promising material for the production of magnetic coils for accelerators, tokamaks and stellarators. Any rare-earth element can be used in ReBCO. Yttrium (YBCO) is the best known, while lanthanum (LBCO), samarium (¹²³Sm), neodymium (¹²³Nd and ⁴²²Nd), gadolinium (¹²³Gd) and europium (¹²³Eu) are also used. The starting materials are brittle, but since 2010, it has been possible to manufacture ReBCO superconductors in bendable tapes.