High-temperature superconductivity

Despite its name, high-temperature superconductivity still occurs at
cryogenic temperatures. The main difference from low-temperature
superconductivity is usually that 'high-Tc' superconductors can use liquid
nitrogen (at 77K) as a coolant while low-temperature superconductors always
need liquid helium (4.2K) temperatures and below.

Most prominent materials in the high-Tc range are the so-called cuprates,
i.e. YBCO (Yttrium-Barium-Copper-Oxide) and related substances.