  The heavy fermion intermetallic compound URu2Si2 exhibits a "hidden-order"
phase below the temperature of 17.5 K, which supports both anomalous metallic
behavior and unconventional superconductivity. While these individual phenomena
have been investigated in detail, it remains unclear how they are related to
each other and to what extent uranium f-electron valence fluctuations influence
each one. Here we use ligand site substituted URu2Si2-xPx to establish their
evolution under electronic tuning. We find that while hidden order is
monotonically suppressed and destroyed for x $\leq$ 0.035, the superconducting
strength evolves through a dome that is centered near $x$ $\approx$ 0.01 and
terminates near $x$ $\approx$ 0.028. This behavior reveals that hidden order
depends strongly on tuning outside of the U f-electron shells. It also suggests
that while hidden order provides an environment for superconductivity and
anomalous metallic behavior, it's fluctuations are not solely responsible for
their progression.
