  In the presence of a magnetic field frustrated spin systems may exhibit
plateaus at fractional values of saturation magnetization. Such plateau states
are stabilized by classical and quantum mechanisms including order-by-disorder,
triplon crystallization, and various competing order effects. In the case of
electrically conducting systems, free electrons represent an incisive probe for
the plateau states. Here we study the electrical transport of Ising-type rare
earth tetraborides $R$B$_4$ ($R=$Er, Tm), a metallic Shastry-Sutherland lattice
showing magnetization plateaus. We find that the longitudinal and transverse
resistivities reflect scattering with both the static and dynamic plateau
structure. We model these results consistently with the expected strong
uniaxial anisotropy in a quantitative level, providing a framework for the
study of plateau states in metallic frustrated systems.
