  We have successfully synthesized the fluo-arsenide SrFeAsF, a new parent
phase with the ZrCuAsSi structure. The temperature dependence of resistivity
and dc magnetization both reveal an anomaly at about T_{an} = 173 K, which may
correspond to the structural and/or Spin-Density-Wave (SDW) transition. Strong
Hall effect and magnetoresistance were observed below T_{an}. Interestingly,
the Hall coefficient R_H is positive below T_{an}, which is opposite to the
cases in the two parent phases of FeAs-based systems known so far, i.e.,
LnFeAsO (Ln = rare earth elements) and (Ba, Sr)Fe_2As_2 where the Hall
coefficient R_H is negative. This strongly suggests that the gapping to the
Fermi surfaces induced by the SDW order is more complex than we believed before
that it removes the density of states on some Fermi pockets and leaves one of
the electron pockets less-gapped or un-gapped. Our data clearly show that it is
possible for the parent phase to have electron-like or hole-like charge
carriers.
