  Understanding iron based superconductors requires high quality impurity free
single crystals. So far they have been elusive for beta-FeSe and extraction of
intrinsic materials properties has been compromised by several magnetic
impurity phases. Herein we report synchrotron - clean beta-FeSe superconducting
single crystals grown via LiCl/CsCl flux method. Phase purity yields evidence
for a defect induced weak ferromagnetism that coexists with superconductivity
below Tc. In contrast to Fe1+yTe - based superconductors, our results reveal
that the interstitial Fe(2) site is not occupied and that all contribution to
density of states at the Fermi level must come from in-plane Fe(1).
