The phrase "sheer authenticity" is correct and usable in written English.
It can be used to emphasize the absolute or unadulterated nature of something's authenticity.
Example: "The artist's work radiates sheer authenticity, capturing the essence of her experiences."
Alternatives: "genuine authenticity" or "absolute authenticity."
The production values you can get there, and the sheer authenticity, feel absolutely amazing.
In such middle-class venues I am hearing a widespread grudging admiration for the Labour leader's sheer authenticity.
In a state that prides itself on its manufactured environments and theme parks, Apalachicola stands out for its sheer authenticity.
How to avoid the lack of authenticity of sheer imitation or mimesis: mimesis of Europe as well as mimesis of one's own artistic tradition.
Sure, one features a bunch of Borscht Belt Jewish comics and the other a crop of suited and booted criminals, but in tone, mood and sheer fly-on-the-wall authenticity, the scenes are cut from the same cloth, and cut - more importantly - by a tailor who knows what he's doing.
So is his sheer orneriness, which betokens a certain authenticity and unwillingness to abide by political convention, such as the one that says that, in American politics, being labelled a socialist is a death sentence.
Their sheer irreverence is taken as sign of authenticity, telling it like it is, no holds barred.
With each evolution of the journey, the requirements for authenticity, joy, creative collaboration and sheer love of life expand and deepen.
Given the sheer crush of news releases, wire services do not generally verify their authenticity, a task impossible under current competitive pressures.
The sheer virtuosity of the men, the gentle femininity of the women, the beauty and authenticity of the costumes, combined in a theatrical experience both thrilling and often moving.
In the heart of San Francisco's vibrant Mexican district, the Mission, simply named La Taqueria is a bastion of authenticity in an increasingly yuppified area that remains popular because of its sheer quality and value for money.
