Samarium cobalt (SmCo5) was the first rare-earth magnet material developed in the early 1960s. Some modern Sm2Co17 grades have the energy of a neodymium magnet but can retain working energies at higher temperatures. They have high field strength, temperature tolerance, and resistance to corrosion.
SmCo magnets are physically hard and chip easily, so they need to be ground before magnetization. They are more suitable for some applications than Neodymium magnets.