Place chicken breast between 2 pieces of plastic wrap. Lightly pound with flat side of meat mallet to 1/2-inch thickness. Remove plastic wrap.
In small bowl stir together chili powder, paprika, salt, cumin and cayenne pepper. Rub on both sides of chicken breast. Place on rack of broiler pan. Broil 4- to 5-inches from heat for 10 to 12 minutes or until no longer pink, turning once. Cool slightly.
In small bowl toss together avocado, tomato and lemon juice. Finely chop chicken. Stir into avocado mixture. Spread about 1/2 teaspoon refried beans on each cracker. Top with chicken mixture. Serve immediately.