Quaternionic extension of the double Taub-NUT metric

Starting from the generic harmonic superspace action of the quaternion-Kähler sigma models and using the quotient approach we present, in an explicit form, a quaternion-Kähler extension of the double Taub-NUT metric. It possesses U(1)×U(1) isometry and supplies a new example of non-homogeneous Einstein metric with self-dual Weyl tensor.