  In one of the sheets in Riemann's Nachlass he defines an entire function and
connect it with his zeta function. As in many pages in his Nachlass, Riemann is
not giving complete proofs. However, I consider that this work is undoubtedly
by Riemann. He obtains an $L^\infty$ function whose Fourier transform vanish at
the real values $\gamma$ with $\zeta(\frac12+i\gamma)=0$. We give proofs of
Riemann formulas. This is an integral representation of the zeta function
different from the known ones. I believe this is the first time it has been
published.
