Short answer: No, unless Unbound.
Long Answer: You have to use Allies. Unlike the Scions that
was mentioning, Skitarii and CultMech are treated as two distinct armies.
Cult Mechanicus has quite a few options to put together a list with:
Battle Congregation: Their own personal take on a CAD, with 1 HQ, 2 troops, and optional units.
Cohort Cybernetica: Formation, 1 HQ and 2 units of Kastelan Robots (with their tech-priests), all played as a single unit.
Elimination Maniple: Formation, 2-3 units of Destroyers, 1-3 units of Kastelans
Numinous Conclave: Formation, lots of Electro Priests
Holy Requisitioner: Formation, 1 HQ and 2-3 units of Breachers
It sounds like you already have Skitarii, so I'll skip them. Basically you can take any of what I listed above (or a CAD, you could technically use that also), and play it side by side with your Skitarii.
Note: The ONLY time that Skitarii will benefit from CultMech powers is if you use a War Convocation, as per White Dwarf 69.