Recent developments in high Tc superconductivity

In this review of recent developments in the area of high Tc have been focussed exclusively on three topics. Cobalt 60 system doped with the alkali metals has opened up an entirely new area of superconductors. Secondly, high Tc superconductivity in Cu-O systems has clearly shown that even a single unit cell is sufficient to show superconductivity. Finally, it has been shown that recent experiments on the critical field behaviour show that the bismuth superconductors may be regarded as being effectively 2-d for most of the range 0 < T < Tc, while in a small range very close to Tc, they appear to show 3-d characteristics. (A.B.)