  Shell model calculations using realistic interactions reveal that the ground
and low-lying yrast states of the $N=Z$ nucleus $^{92}_{46}$Pd are mainly built
upon isoscalar neutron-proton pairs each carrying the maximum angular momentum
J=9 allowed by the shell $0g_{9/2}$ which is dominant in this nuclear region.
This structure is different from the ones found in the ground and low-lying
yrast states of all other even-even nuclei studied so far. The low-lying
spectrum of excited states generated by such correlated neutron-proton pairs
has two distinctive features: i) the levels are almost equidistant at low
energies and ii) the transition probability $I\rightarrow I-2$ is approximately
constant and strongly selective. This unique mode is shown to replace normal
isovector pairing as the dominating coupling scheme in $N=Z$ nuclei approaching
the doubly-magic nucleus $^{100}$Sn.
