Riemannian almost-product structures with maximal mobility

The aim of the paper is to give a classification up to isomorphism of (local or simply-connected global) Riemannian almost-product structures (i.e. O(n ₁) × ... × O(n _t)-structures) whose automorphism group has maximal dimension (the so-called -structures). The describing objects are Lie algebras with some additional structure, and the methods are mainly Lie algebraic. The results obtained are applied to determine all -structures on simply-connected spaces of constant curvature.