Trim and peel carrots and sweet potatoes. Cut into 3/4 inch slices and cook in boiling salted water until tender, about 10 minutes. Drain and chill quickly in ice water. Drain and pat dry. In shallow heatproof 13X9 in. Casserole, overlap slices of potato around outside of dish. Arrange carrots in center. In small saucepan, combine sugar, orange juice, butter, orange rind, cinnamon, nutmeg and coriander. Heat gently until butter is melted and dissolved. Remove from heat; stir in liqueur, and salt and pepper to taste. Drizzle over vegetables and sprinkle with pecans. (Vegetables can be prepared in advance to this point. Let cool, cover and refrigerate for 4 to 5 hours.) Bake in 450F oven for 20 minutes (25 minutes if vegetables are cold), basting occasionally with orange syrup. For crusty topping, broil for 1 to 2 minutes.