  We report the magnetotransport characteristics of a trilayer ferromagnetic
tunnel junction build of an electron doped manganite (La_0.7Ce_0.3MnO_3) and a
hole doped manganite (La_0.7Ca_0.3MnO_3). At low temperatures the junction
exhibits a large positive tunneling magnetoresistance (TMR), irrespective of
the bias voltage. At intermediate temperatures below T_C the sign of the TMR is
dependent on the bias voltage across the junction. The magnetoresistive
characteristics of the junction strongly suggest that La_0.7Ce_0.3MnO_3 is a
minority spin carrier ferromagnet with a high degree of spin polarization, i.e.
a transport half metal.
