We apply the machinery of relative tensor triangular Chow groups to the
action of the derived category of quasi-coherent sheaves on a noetherian scheme
$X$ on the derived category of quasi-coherent $\mathcal{A}$-modules, where
$\mathcal{A}$ is a (not necessarily commutative) quasi-coherent
$\mathcal{O}_X$-algebra. When $\mathcal{A}$ is commutative and coherent, we
recover the tensor triangular Chow groups of the relative Spec of
$\mathcal{A}$. We also obtain concrete descriptions for integral group algebras
and hereditary orders over curves, and we investigate the relation of these
invariants to the classical ideal class group of an order. An important tool
for these computations is a new description of relative tensor triangular Chow
groups as the image of a map in the K-theoretic localization sequence
associated to a certain Verdier localization.Comment: 39 pages; all comments welcom