The term 
high-temperature superconductor was initially employed to designate the new family of cuprate-perovskite 
ceramic materials discovered by 
J.G. Bednorz[?] and 
K.A. Mueller[?] in 1986. These materials are characterized by presenting 
superconductivity at a higher temperature than 
conventional superconductors (which require temperatures a few degrees above absolute zero), and by other 
unconventional features. Recently, other 
unconventional superconductors 
have been discovered. Some of them also have unusually high values of the critical temperature 
Tc, and hence they are sometimes also called high-temperature superconductors, although the record is still held by a cuprate perovskite material (
Tc=133
K, that is -140
°C). Nevertheless it is widely believed that if 
room temperature superconductivity[?] is ever achieved it will be in a different family of materials.
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