  Cleavable metallic antiferromagnets may be of use for low-dissipation
spintronic devices; however, few are currently known. Here we present
orthorhombic MnRhBi3 as one such compound and present a thorough study of its
physical properties. Exfoliation is demonstrated experimentally, and the
cleavage energy and electronic structure are examined by density functional
theory calculations. It is concluded that MnRhBi3 is a van der Waals layered
material that cleaves easily between neighboring Bi layers, and that the Bi
atoms have lone pairs extending into the van der Waals gaps. A series of four
phase transitions are observed below room temperature, and neutron diffraction
shows that at least two of the transitions involve the formation of
antiferromagnetic order. Anomalous thermal expansion points to a
crystallographic phase transition and/or strong magnetoelastic coupling. This
work reveals a complex phase evolution in MnRhBi3 and establishes this
cleavable antiferromagnetic metal as an interesting material for studying the
interplay of structure, magnetism, and transport in the bulk and ultrathin
limits as well as the role of lone pair electrons in interface chemistry and
proximity effects in van der Waals heterostructures.
