The growth rates for pure Artin groups of dihedral type

We consider the kernel of the natural projection from the Artin group of dihedral type I2(k)I2(k) to the associated Coxeter group, which we call a pure Artin group of dihedral type and write PI2(k)PI2(k). We show that the growth rates for both the spherical growth series and geodesic growth series of PI2(k)PI2(k) with respect to a natural generating set are Pisot numbers.