  We characterize the low-energy physics of the two-orbital Hubbard model in
the orbital-selective Mott phase, in which one band is metallic and the other
insulating. Using dynamical mean-field theory with the numerical
renormalization group at zero temperature, we show that this phase has a
ferromagnetic instability for any nonzero Hund's rule exchange interaction,
which can be understood in terms of an effective spin-1 Kondo Hamiltonian. The
metallic band therefore behaves as a singular Fermi liquid for which the
self-energy has a logarithmic singularity at the Fermi energy.
