  Altermagnetism has emerged as a third type of collinear magnetism. In
contrast to standard ferromagnets and antiferromagnets, altermagnets exhibit
extra even-parity wave spin order parameters resulting in a spin-splitting of
electronic bands in momentum space. In real space, sublattices of opposite spin
polarization are anisotropic and related by rotational symmetry. In the
hitherto identified altermagnetic candidate materials the anisotropies arise
from the local crystallographic symmetry. Here, we show that altermagnetism can
also form as an interaction-induced electronic instability in a lattice without
the crystallographic sublattice anisotropy. We provide a microscopic example of
a two-orbital model showing that the coexistence of staggered antiferromagnetic
and orbital order can realize robust altermagnetism. We quantify the
spin-splitter conductivity as a key experimental observable and discuss
material candidates for the interaction-induced realization of altermagnetism.
