The phrase "at once unique" is correct and usable in written English.
It can be used to describe something that is simultaneously distinctive and exceptional in nature.
Example: "The artist's style is at once unique and reminiscent of classical techniques, making her work stand out in the contemporary art scene."
Alternatives: "simultaneously distinctive" or "both original and exceptional".
The Rubins, and their assorted foibles, flaws and neuroses, are at once unique and utterly recognisable.
One of the curious aspects of cultural memory in an age of mass culture is that specific moments and experiences are at once unique and interchangeable.
"Our trials and triumphs became at once unique and universal, black and more than black," Mr. Obama wrote in his autobiography "Dreams From My Father".
Bai Yilou's hand-stitched collage of photographic portrait negatives suggests the dense, roiling diversity of China's population, in which everyone is at once unique and anonymous.
Pääbo estimates that when the Neanderthal Genome Project is completed, the list of base-pair changes that are at once unique to humans and shared by all humans will number around a hundred thousand.
The work of the New York photographer Helen Levitt, who has died aged 95, is at once unique and typical, born of the flowering of "documentary expressionism" in 1930s America.
Once in a while, however, might we not reasonably be asked to look at them as a unique and perfect entity, rather than a chapter between chapters?
The result is a 3D printing assembly line: many products printing at once, all unique, all in full color and multi materials.
There was something extra to be seen and heard, which offered at once a unique form of entertainment and sentimentality.
The religious and political activities in Pennsylvania during the period between the Great Awakening and the eve of the Revolution (1740-1770) were at once typical and unique: typical as far as he general trend of American experience is concerned, unique, however, with regard to the participants and many of the issues at stake.
It's an extreme work, at once startling and unique.
