Preheat the oven to 220 degrees C. Use a zester to remove the rind from the orange, or grate finely. Squeeze the juice into the same bowl.
Chop the sage leaves and combine with the orange juice and zest, marmalade, oil and pepper.
Place the veal and the garlic, whole and unpeeled, in a lightly oiled baking dish. Baste the veal with the orange mixture, being sure to coat the rack thoroughly, then cook in the oven for 20 minutes.
Move the baking dish from the oven to the stove top and transfer the veal to a serving platter; allow to rest in a warm place. Meanwhile, add the sherry and stock to the garlic in the baking dish and cook, stirring, over moderately high heat for 2–3 minutes, until the sauce has reduced and thickened slightly.
To serve, carve the veal into individual chops and spoon over the garlic and pan juices.