  We suggest that a spin-charge separating ansatz, leading to non-Abelian
$SU(2) \otimes U_S(1)$ gauge symmetries in doped antiferromagnets, proposed
earlier as a way of describing Kosterlitz-Thouless superconducting gaps at the
nodes of the gap of d-wave (high-T_c) superconductors, may also lead to a
pseudogap phase, characterised by the formation of (non-superconducting)
pairing and the absence of phase coherence. The crucial assumption is again the
presence of electrically charged Dirac fermionic excitations (holons) about the
points of the (putative) fermi surface in the pertinent phase of the
superconductor. We present arguments in support of the r\^ole of
non-perturbative effects (instantons) on the onset of the pseudogap phase. As a
means of probing such gauge interactions experimentally, we perform a study of
the scaling of the thermal conductivity with an externally-applied magnetic
field, in certain effective models involving gauge and/or four-fermion
(contact) interactions.
