U(1)xU(1) quaternionic metrics from harmonic superspace

We construct, using harmonic superspace and the quaternionic quotient approach, a quaternionic-Kaehler extension of the most general two centres hyper-Kaehler metric. It possesses U(1)xU(1) isometry, contains as special cases the quaternionic-Kaehler extensions of the Taub-NUT and Eguchi-Hanson metrics and exhibits an extra one-parameter freedom which disappears in the hyper-Kaehler limit. Some emphasis is put on the relation between this class of quaternionic-Kaehler metrics and self-dual Weyl solutions of the coupled Einstein-Maxwell equations. The relation between our explicit results and the recent general ansatz of Calderbank and Pedersen for quaternionic-Kaehler metrics with U(1)xU(1) isometries is traced in detail