Use diode in parallel to increase current
Those diodes are peak catchers and hence can have a momentary rating far in excess of average current rating. Read the appropriate data sheet. Also, the L298 is fairly crappy and I reckon you'd burn that first before damaging a diode. Same advice read the data sheet and note the power dissipation OR go to my profile page and find a question and answer I raised on low voltage H bridges that explains the problems.