Preheat the oven to 400 degree F. Line a large baking sheet with parchment paper.
Heat a charcoal or gas grill until hot (you should barely be able to hold your hand 3 or 4 inches from the fire), or use a grill pan or medium-sized skillet on medium-high heat.
Bring the steak to room temperature, pat dry with paper towels, and sprinkle both sides with salt and pepper.
Wash and peel the potatoes, and cut into 1/4-inch-thick slices or cut into wedges. Toss with the olive oil and 1/4 teaspoon each salt and freshly ground pepper. Arrange the potatoes in a single layer on the baking sheet, and bake for 25 to 30 minutes. Turn and continue baking for 10 to 15 minutes more or until golden brown and tender.
Meanwhile, grill the steak until nicely browned, 3 to 4 minutes per side. Move the meat to a cooler part of the grill and cook for another 5 to 7 minutes, turning once. Cover and let rest for 5 minutes before cutting across the grain into thin slices. Serve with sweet potatoes.