I don't believe in 47 Ohm @ ( 12 V - 2*1.3 V ) This would give 190 mA, far beyond the max 50 mA.
Either the datasheet does not fit, or it's not 12V, or it's not 47 Ohms.
Easiest solution: use a 1k pot, start at 1k, and see when you have sufficient brightness.
If the leds really start shining at about 1.2V and 15 mA is a proper current (according to your datasheet) ,
you can easily run them in series with a 200 .. 300 Ohms resistor at 5V.