  We have investigated the ferromagnetic (FM) phase which suddenly develops in
UCo1-xRuxAl and is isolated by paramagnetic regions on both sides from the
parent UCoAl and URuAl. For that purpose we have grown high quality single
crystals with x = 0.62, 0.70, 0.74, 0.75 and 0.78. The properties of the FM
phase have been investigated by microscopic and macroscopic methods. Polarized
neutron diffraction on a single crystal with x = 0.62 revealed the gradual
growth of the hybridization between U and T-site in the U - T plane with
increasing x. Hybridization works here as a mediator of the strong indirect
interaction, while the delocalized character of the 5 f states is still
conserved. As a result very weak spontaneous magnetic moments are observed for
all alloys with magnitude nearly in proportion to the TC for x < 0.62, while an
enormous disproportion exists between them near xcrit.. The magnetization,
specific heat, electrical resistivity, and Hall effect measurements confirmed
that the FM transition is suppressed continuously at the critical concentration
xcrit. = 0.77. Two quantum critical points are then expected on both sides of
the FM dome. We propose a scenario that the order of the FM/PM transition
differs at opposite boundaries of the FM dome. We conclude that both
criticalities are influenced by disorder. Criticality on the UCoAl side has the
character of a clean FM metal, while on the Ru rich side it has the character
of a magnetically inhomogeneous system involving a Griffiths phase.
