We study the combinatorics of a subcomplex of the Bloch–Kriz cycle complex that
was used to construct the category of mixed Tate motives. The algebraic cycles we
consider properly contain the subalgebra of cycles that correspond to multiple
logarithms (as defined by Gangl, Goncharov and Levin). We associate an algebra of
graphs to our subalgebra of algebraic cycles. We give a purely combinatorial criterion
for admissibility. We show that sums of bivalent graphs correspond to coboundary
elements of the algebraic cycle complex. Finally, we compute the Hodge
realization for an infinite family of algebraic cycles represented by sums of
graphs that are not describable in the combinatorial language of Gangl et
al.