Pisot numbers, primitive matrices and beta-conjugates. We show that given a Pisot number β, for any integer n large enough, there is a nonnegative primitive square matrix whose order is equal to the degree of β, and the matrix admits β for eingenvalue. Let β = a1/β + a2/β + · · ·+ an/β + · · · be the β-expansion of β. For any Pisot number β, the sequence (an)n≥1 is ultimately periodic i.e., for...