Then you need a MOSFET H-bridge that will run at 5V, and add a 0.33 ohm resistor in series with the coil
so it gets 4V.
Simple BJTs don't have the (saturation) current gain to drive 3A from an Arduino pin.
Alternatively you could rework the darlington bridge to work from about 7.5 to 8V, with level shifting to the high
side drivers.