The phrase "an unexpected combination of" is correct and usable in written English.
You can use it when describing a surprising or unusual mix of elements, ideas, or characteristics.
Example: "The dish was an unexpected combination of sweet and savory flavors that delighted the diners."
Alternatives: "a surprising blend of" or "an unusual mix of".
"It was an unexpected combination of energies," muses Morley, ever the pop theorist.
"To compensate for that loss, I use an unexpected combination of materials".
The day she died, I experienced such an unexpected combination of emotions that I thought I was, clinically, in shock.
The best style is almost always a result of an unexpected combination of good and less costly things, of masculine and feminine elements, with a sharp eye toward what's in fashion.
Instead, it was an unexpected combination of attacks on Romney, Obama's positive four-year record – Osama's name may have been mentioned more over the course of the night than Obama's – and a relatively brief list of voter-getter issues.
The tune descended to an unexpected combination of notes at the end of each refrain, and the simplicity and strength and heart with which she sang stopped the whole of the Hue-Man Bookstore in its tracks.
Even humble chicken breast is tender and flavorful here, glazed with lemon, rolled around fennel and served with a fine, unexpected combination of wild rice and Savoy cabbage.
Songs have become, for lack of a better word, trivial: not through any less effort from the best musicians, but through the unexpected combination of a nearly infinite supply, constant availability, suboptimum sound quality and the intangibility I've always thought I would welcome.
Though it is slightly incongruous to pad out a Jacobean drama with supplementary material by Burt Bacharach, the unexpected combination of easy-listening and difficult-watching makes a striking disjunction nonetheless.
A study in contrasts, this salad blew us away with its unexpected combination of flavors and textures.
Throughout the ballet, and amid all the cliches, there was the unexpected combination of steps.
