  We report high field magneto transport of Sm/PrFeAsO. Below spin density wave
transition (TSDW), the magneto-resistance (MR) of Sm/PrFeAsO is positive and
increasing with decreasing temperature. The MR of SmFeAsO, is found 16%,
whereas the same is 21.5% in case of PrFeAsO, at 2.5 K under applied magnetic
field of 14 Tesla (T). In case of SmFeAsO, the variation of isothermal MR with
field below 20 K is nonlinear at lower magnetic fields (< 2 Tesla) and the same
is linear at moderately higher magnetic fields (H \geq 3.5 T). On the other
hand PrFeAsO shows almost linear MR at all temperatures below 20 K. The
anomalous behavior of MR being exhibited in PrFeAsO is originated from Dirac
cone states. The stronger interplay of Fe and Pr ordered moments is responsible
for this distinct behavior. PrFeAsO also shows a hump in resistivity (R-T) with
possible conduction band (FeAs) mediated ordering of Pr moments at around 12 K.
However the same is absent in SmFeAsO even down to 2 K. Our results of high
field magneto-transport of up to 14 Tesla brings about clear distinction
between ground states of SmFeAsO and PrFeAsO.
