  We construct the systems of bi-orthogonal polynomials on the unit circle
where the Toeplitz structure of the moment determinants is replaced by $
\det(w_{2j-k})_{0\leq j,k \leq N-1} $ and the corresponding Vandermonde modulus
squared is replaced by $ \prod_{1 \le j < k \le N}(\zeta^{2}_k -
\zeta^{2}_j)(\zeta^{-1}_k - \zeta^{-1}_j) $. This is the simplest case of a
general system of $pj-qk$ with $p,q$ co-prime integers. We derive analogues of
the structures well known in the Toeplitz case: third order recurrence
relations, determinantal and multiple-integral representations, their
reproducing kernel and Christoffel-Darboux sum, and associated
(Carath{\'e}odory) functions. We close by giving full explicit details for the
system defined by the simple weight $ w(\zeta)=e^{\zeta}$, which is a
specialisation of a weight arising from averages of moments of derivatives of
characteristic polynomials over $USp(2N)$, $SO(2N)$ and $O^-(2N)$.
