Specific heat of high temperature superconductors in high magnetic fields

We review investigations of the mixed-state specific heat (C) of extreme type-II superconductors in magnetic fields B less than or equal to 16 T, from 1 K to T-c. In YBa2Cu3Ox (Y123) at low temperature T, a scaling law Delta C proportional to(TB1/2)f(T/B-1/2), which is a signature of d-wave symmetry, is observed for the background-free anisotropic component Delta C=C(B//c)-C(B//ab). At intermediate T, a C(B)-C(0)proportional to T(n)BlnB behaviour, which may be explained by the London model, smoothly sets in. Near T-c, superconducting fluctuations are investigated using the background-free derivative partial derivative(C/T)partial derivative B. 3D-XY scaling properties are verified up to the overdoped regime. Fluctuations obey different laws in Bi2Sr2CaCu2Ox (Bi2212), which is strongly affected by its 2D character. Finally, the melting line of the vortex solid, which is now believed to be the only true phase transition above H-cl in the presence of fluctuations, is observed in Y123 either as a 1st- or 2nd-order transition, depending on pinning.