Existence of color sextet diquark Higgs fields with TeV masses will indicate a fundamentally different direction for unification than conventional grand unified theories. One class of models where they appear naturally is the supersymmetric SU(2)(L)xSU(2)(R)xSU(4)(c) model embedding the seesaw mechanism for neutrino mass with seesaw scale around 10(11) GeV. The diquark Higgs fields in this model couple only to up-type quarks. We discuss phenomenological constraints on these fields and show that they could be detected at LHC via their decay to either tt or single top+jet. We also find that existing Tevatron data gives a lower bound on its mass somewhere in the 400-500 GeV, for reasonable values of its coupling.