3D Fermi Surface Mapping of Ce$_2$RhIn$_8$*

Photon-dependent multi-Brillouin zone angle-resolved photoemission (ARPES) measurements are presented for the antiferromagnet heavy fermion bilayer compound Ce$_2$RhIn$_8$. Highly automated Fermi Surface (FS) mapping for excitation energies of 90-120 eV allow visualization of k$_z$-variations of the electronic structure and permit a k$_z$-tomographic determination of the three-dimensional (3D) FS topology with sufficient detail for quantitative comparison to dHvA orbit areas and LDA-predicted topological shapes. In addition to confirming the quasi-2D circular and square topologies centered on the Brilluoin zone corner, highly 3D k$_z$-variations are observed along the (100) directions $\Gamma$-X (Z-R). Results are compared to a similar ARPES determination of the 3D electronic structure and FS of the single layer compound CeCoIn$_5$.