Yukawa couplings in a model with gauge, Higgs and matter unification

We discuss how unification of the gauge, Higgs and (three chiral family) matter superfields can be realized from the compactification of a six-dimensional supersymmetric SU(8) gauge theory over the orbifold R4×T2/Z3. The bulk gauge interaction includes Yukawa interactions to generate masses for quarks and leptons after the electroweak symmetry is broken. The Yukawa matrices in this case turn out to be antisymmetric, and thus not phenomenologically viable. To overcome this we introduce brane fields which are vector-like under the Standard Model gauge symmetry, and so do not alter the number of chiral families. In such a setup, the observed fermion masses and mixings can be realized by taking into account suppression effects from the effective Wilson line couplings and large volume of the extra dimensions.