The U -polynomial of Noble and Welsh is known to have intimate connections with the Potts model as well as with several important graph polynomials. For each graph G, U (G) is equivalent to Stanley's symmetric bad colouring polynomial XB(G). Moreover Sarmiento established the equivalence between U and the polychromate of Brylawski. Loebl defined the q-dichromate Bq(G, x, y) as a function of a graph G and three independent variables q, x, y, proved that it is equal to the partition function of the Potts model with variable number of states and with a certain external field contribution, and conjectured that the q-dichromate is equivalent to the U -polynomial. He also proposed a stronger conjecture on integer partitions. The aim of this paper is two-fold. We present a construction disproving Loebl's integer partitions conjecture, and we introduce a new function Br,q(G; x, k) which is also equal to the partition function of the Potts model with variable number of states and with a (different) external field contribution, and we show that Br,q(G; x, k) is equivalent to the U -polynomial and to Stanley's symmetric bad colouring polynomial.This completes the proof of the claim, and hence B r,q determines XB, completing the proof of the theorem.As a corollary we obtain the equivalence of B r,q and U .Corollary 2. Let r > 1 be given. Then graph functions B r,q and U are equivalent.Proof. This follows from Theorem 1, and Theorem 6.2 of [6] which gives the equivalence of U and XB.