  It is shown that AdS(5)xS(5) supergravity has hitherto unnoticed
supersymmetric properties that are related to a hidden 12-dimensional
structure. The totality of the AdS(5)xS(5) supergravity Kaluza-Klein towers is
given by a single superfield that describes the quantum states of a
12-dimensional supersymmetric particle. The particle has super phase space
(X,P,Theta) with (10,2) signature and 32 fermions. The worldline action is
constructed as a generalization of the supersymmetric particle action in
Two-Time Physics. SU(2,2|4) is a linearly realized global supersymmetry of the
2T action. The action is invariant under the gauge symmetries Sp(2,R),
SO(4,2),SO(6), and fermionic kappa. These gauge symmetries insure unitarity and
causality while allowing the reduction of the 12-dimensional super phase space
to the correct super phase space for AdS(5)xS(5) or M(4)xR(6) with 16 fermions
and one time, or other dually related one time spaces. One of the predictions
of this formulation is that all of the SU(2,2|4) representations that describe
Kaluza-Klein towers in AdS(5)xS(5) or M(4)xR(6) supergravity universally have
vanishing eigenvalues for all the Casimir operators. This prediction has been
verified directly in AdS(5)xS(5) supergravity. This suggests that the
supergravity spectrum supports a hidden (10,2) structure. A possible duality
between AdS(5)xS(5) and M(4)xR(6) supergravities is also indicated.
Generalizations of the approach applicable 10-dimensional super Yang Mills
theory and 11-dimensional M-theory are briefly discussed.
