  Gapless electronic systems containing topologically nontrivial Fermi points
are sources of various topological insulators. Whereas most of these special
band-crossing points are built in the electronic structure of the
non-interacting lattice models, we show that a quadratic Fermi point
characterized by a non-zero winding number emerges with a collinear triple-Q
spin-density-wave state that arises from a perfectly nested but topologically
trivial Fermi surface. We obtain a universal low-energy Hamiltonian for the
quadratic Fermi point and show that such collinear orderings are unstable
against the onset of scalar spin chirality that opens a gap and induces a
spontaneous quantum Hall insulator as the temperature tends to zero.
