  The 4f crystal-electric field ground state wave functions of
CeRh(1-x)Ir(x)In5 have been determined by linear polarization dependent soft
x-ray absorption spectroscopy (XAS) at T = 8 K. We demonstrate that these
ground state wave functions correlate with the phase diagram of the
substitution series, which covers long-range antiferromagnetic order,
unconventional superconductivity, and coexistence of these two states. We
discuss how certain wave functions could affect magnetic order and anisotropic
hybridization, facilitating the formation of a superconducting ground state at
low temperatures.
