Use a mandolin (optional) to cut sweet potatoes into 1/8-inch thick slices. (A 12-ounce potato yields about 30 slices.) Heat 4 Tbs. olive oil in a 12-inch skillet over medium heat. In small batches, add sweet-potato slices to skillet (and oil as needed) and cook for two to three minutes per side or until browned. Remove chips from skillet and place on a paper towel to drain; sprinkle lightly with salt and pepper while warm.
In a medium bowl, mix together mango, tomatoes, red onion, cilantro, and lime juice. Season with salt and pepper.