2x5km at 10km, HM or Marathon pace?

Just feel the right pace. If you ask me: I like 2 x 5k early on in a training phase at MP or even a tad slower. Later on I like do do it more like HMP. Or start rep 1 at MP and progress the second rep to HMP. 2 x 5k at 10k pace would be almost impossible for me in training.

Also depends on how fast you are. When your a 3:30 marathoner and 1:37 half marathoner it could be that your able to run relatively faster than a 2:30/1:10 or 2:07/1:00 type of runner :)

Pikachu

2x5k at HMP is a fine tempo for HM purposes. Anything faster and you are leaving your race out there. But you have to build up to that, probably with tempo cruise intervals, 3x1 > 4x1 > 5x1 > 3x2 > 2x3.

I'm not fast,

10K pace 3:50/km

HM pace 4:02/km

Mara pace 4:15/km

Thanks for the comments, I might do a couple at marathon pace then then try HM pace.

Figure out what you think you could do 30 km at. That intermediate pace is the one that will help you and give you a bit of a speed cushion on race day.

Around 4:10 pace.