A detailed magnetotransport study of novel heterostructures comprised of epitaxial layers of semimetallic ErAs buried inside GaAs displays a cusplike anomaly in the magnetoresistance that is caused by spin-disorder scattering at the antiferromagnetic-paramagnetic phase boundary. The relatively low carrier concentration spares the Fermi surface from being cut by the broken symmetry and only spin disorder contributes to the anomaly.

• Received 19 January 1989

DOI:https://doi.org/10.1103/PhysRevLett.62.2309