Exact T-duality between Calorons and Taub-NUT spaces

We determine all SU(2) caloron solutions with topological charge one and arbitrary Polyakov loop at spatial infinity (with trace 2.cos(2.pi.omega)), using the Nahm duality transformation and ADHM. By explicit computations we show that the moduli space is given by a product of the base manifold R^3 X S^1 and a Taub-NUT space with mass M=1/sqrt{8.omega(1-2.omega)}, for omega in [0, 1/2], in units where S^1=R/Z. Implications for finite temperature field theory and string duality between Kaluza-Klein and H-monopoles are briefly discussed