Squeeze juice from half the lime into a large bowl; add 1 teaspoon olive oil, 1/2 teaspoon chili powder and 1/4 teaspoon of salt; stir well with a whisk. Add beans, corn, tomatoes, scallions, and cilantro; toss gently to combine. Stir in cooked rice, and toss until thoroughly combined. Cover loosely and keep warm while preparing scallops.
Combine remaining 1 teaspoon olive oil, 1/2 teaspoon chili powder, and 1/4 teaspoon salt in a large bowl. Pat scallops dry with a paper towel, and toss in the oil mixture until thoroughly coated. Squeeze 2 teaspoons juice from remaining lime half and set aside.
Heat a large nonstick skillet over medium-high heat. Place 1 scallop in center of pan. When scallop sizzles, arrange remaining scallops in pan, flat sides down (make sure they arenï¿½t touching or they will steam, not sear properly). Cook 2 to 3 minutes on each side until lightly browned and opaque in the center. Drizzle scallops with lime juice, and toss gently to coat. Divide salad into 4 servings and top with 4 scallops each. Serve immediately.