Polyphase decomposition of IIR filter
Using matlabs tf2cl, it may require the DSP toolbox, you can turn the transsfer function (numerator and denominator coefficients) in to a cascade allpass lattice coefficients, which is a two phase filter.

% Generate some IIR filter coefficients
[b,a]=cheby1(9,.5,.4);

% Coupled allpass decomposition
[k1,k2]=tf2cl(b,a);