  We present the first report on a large low-temperature magnetoresistance (MR)
of more than 1600% in a SrFe2As2 single crystal and 1300% in a low-energy Ca
ion-implanted SrFe2As2 single crystal that occurs before the emergence of
crystallographic strain-induced bulk superconductivity arising from a sample
aging effect. In accordance to band structure calculations from literature,
which consitently show more than 2 bands are involved in the transport, we have
modeled this large MR at high fields using a 3-carrier scenario rather than
solely on quantum linear MR model generally used to explain the MR in
iron-pnictides. At and below 20 K the large MR may be due to 3-carrier
transport in an inhomogeneous state where there are superconducting and
metallic regions.
