Line a 9x13 pan with layer of parchment paper. Melt sugar and syrup until bubbly, do not boil. Remove from heat, stir in peanut butter. Mix mixture with rice krispies. Press mixture in pan and let firm up. Melt chips together in microwave safe bowl, 30 seconds at a time. Spread on top. Chill about 15 minutes to set chocolate. Pull out of pan by edge of parchment paper and cut into squares. Serve room temperature.