  Geometrically frustrated magnetic systems, such as those based on the
Shastry-Sutherland lattice, offer a rich playground for exploring
unconventional magnetic states. The delicate balance between competing
interactions in these systems leads to the emergence of novel phases. We
present the characterization of Er2Be2GeO7, an SSL compound with Er3+ ions
forming orthogonal dimers separated by non-magnetic layers. Neutron scattering
reveals an antiferromagnetic dimer structure at zero field, typical of Ising
spins on that lattice and consistent with the anisotropic magnetization
observed. However, magnetization measurements exhibit fractional plateaus at
1/4 and 1/2 of saturation, by contrast to the expected 1/3 plateau of the SSL
Ising model. We show that this behaviour requires spatially anisotropic
interactions, and, using a tensor network approach, we show that all
properties, including thermodynamics, can be quantitatively explained by an
Anisotropic Shastry-Sutherland Ising Model whose microscopic origin can be
traced back to Dzyaloshinskii-Moriya interactions. This study highlights
Er2Be2GeO7 as a promising platform for investigating exotic magnetic phenomena
and potential applications in spintronics.
