  We study the magnetotransport in small hybrid junctions formed by
high-mobility GaInAs/InP heterostructures coupled to superconducting (S) and
normal metal (N) terminals. Highly transmissive superconducting contacts to a
two-dimensional electron gas (2DEG) located in a GaInAs/InP heterostructure are
realized by using a Au/NbN layer system. The magnetoresistance of the S/2DEG/N
structures is studied as a function of dc bias current and temperature. At bias
currents below a critical value, the resistance of the S/2DEG/N structures
develops a strong oscillatory dependence on the magnetic field, with an
amplitude of the oscillations considerably larger than that of the reference
N/2DEG/N structures. The experimental results are qualitatively explained by
taking Andreev reflection in high magnetic fields into account.
