  Novel ferromagnetism in Ca$_{1-x}$La$_{x}$B$_6$ is studied in terms of the
Ginzburg-Landau theory for excitonic order parameters, taking into account
symmetry of the wavefunctions. We found that the minima of the free energy
break both inversion and time-reversal symmetries, while the product of these
two remains preserved. This explains various novelties of the ferromagnetism
and predicts a number of magnetic properties, including the magnetoelectric
effect, which can be tested experimentally.
