Reissner-Nordstr\"om Type Black Holes in Dilaton-Axion Gravity

A $2p+5$ parametric family of black holes is constructed in dilaton–axion gravity with $p$ vector fields using a holomorphic representation of U–duality in three dimensions. The metric of the non–extremal black holes has a Reissner–Nordstr"om type structure and generically possesses an internal horizon. However in the extremal limit the generic solution exhibits a dilatonic type null singularity. Only in the case of the orthogonal electric and magnetic charges (if $p>1$) the extremal solution may have a non–singular event horizon.