In a large mixing bowl, beat sugar and eggs until thick and pale.
Add oil, butter, and vanilla, beating until combined.
Add sweet potato, beating until just combined.
In a large bowl, whisk together flour, baking powder, baking soda, salt, cinnamon, pumpkin pie spice, and ground clove.
Gradually add the flour mixture alternately with the buttermilk to the sweet potato mixture in the mixing bowl, beginning and ending with the flour mixture.
Beat until just combined after each addition.
Spread batter into a greased bundt pan.
Bake at 350 degrees for 50-60 minutes, or until edges are golden, and a toothpick inserted near the center comes out clean.
Cool in pan for 20 minutes.
Loosen edges of cake carefully with a knife, and invert cake onto a serving plate.