No.
But I think they can use spellstrike to deliver a touch ranged spell using it.
[Edited for clarity and rules terminology]
^Most Magi can't do that either. Spellstrike only works with melee attacks unless you took an archetype that makes it ranged (Eldritch Archer and Card Caster versions of Spellstrike are only ranged or thrown, respectively, and Myrmidarch gets both (melee and ranged), although the ranged versions that Card Caster and Myrmidarch get are of limited use due to not getting a thrown/ranged version of Spell Combat (which Eldritch Archer gets, but then loses melee Spell Combat(*)).
(*)Although I wonder if an Eldritch Archer who somehow managed to get hold of Bowstaff, which is not normally on any arcane spellcasting list, could actually do melee Spell Combat after all, since the modified ability just says that you have to use a ranged weapon; also note that an Eldritch Archer doesn't get Use Magic Device in class.
Darn it, I shouldn't have edited the way I did.
Because sharding is allowed "with the weapon in place of any melee attack", the free melee attack a magus gets from spellstrike, which is a melee attack with the weapon, can use the sharding property, even though it is a "special ranged attack".
That's my read, anyway, and how I'd run it at my table. I'm quite willing to be proven wrong.
Interesting take on it . . . I wonder if this needs a FAQ.
The wielder of a sharding weapon can make a special ranged attack with the weapon in place of any melee attack.
As a full-round action, he can make all of his attacks with his melee weapon at a –2 penalty and can also cast any spell from the magus spell list with a casting time of 1 standard action (any attack roll made as part of this spell also takes this penalty).
Huh. This works even more than I thought it did originally. With Spell Combat's wording, you "make attacks with [your] melee weapon" which...you technically still are. The shard attack is an attack with your melee weapon.
This would be awesome for a Myrmidarch Magus, since now they can switch hit Spellstrike with the same weapon.