PLTDEV.

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UGA X (LR25) INBOUND TO SDF AT 17000 FT. ACR Y (SF34) 16000 FT CHH TO BNA. UGA X 17900 FT DSNDING TO 17000 FT REQUEST LOWER ALT; TFC CALLED 12 O'CLOCK 10 MI. AT 16000 FT ACR Y LOWER CLRING TFC. SECONDS LATER ACR Y ADVISED HE WAS CLBING IN RESPONSE TO AN 'RA' ALERT. ACFT WERE OBSERVED 1 MI APART BOTH MODE C READOUT SHOWING 16000 FT. UGA X WAS ASKED AND VERIFIED AT 17000 FT. ACR Y STATED 'NO WAY' TO THAT AND SAID HE HAD HIM VISUALLY AND WAS CLR. SUPPLEMENTAL INFO FROM ACN 288306: THE CAPT AND I NOTICED AN ACFT ON TCASII AT OUR SAME ALT (16000 FT MSL) AND CLOSING. BEFORE WE COULD GET A VISUAL; AND BEFORE ATC ISSUED A TA; WE GOT A RA FROM TCASII INDICATING A 2000 FPM CLB. AT THIS TIME I DISENGAGED THE AUTOPLT AND INITIATED A CLB IN ACCORDANCE WITH THE TCASII. ATC WAS ADVISED OF THE RA AND OUR EVASIVE ACTION. ATC ASKED THE OTHER ACFT (A LEAR) WHICH ALT HE WAS AT AND HE RESPONDED 17000 FT. WHEN WE FINALLY GOT A VISUAL ON THE ACFT WE WERE AT 16700 FT AND THE LEAR PASSED BELOW US FROM L TO R. ATC ASKED US IF WE FINALLY HAD VISUAL AND WE ACKNOWLEDGED AFFIRMATIVE AND WE WERE GIVEN THE COMMAND BY ATC TO 'MISS HIM.' AFTER THE INCIDENT ATC INSTRUCTED THE LEAR TO CONTACT QUALITY ASSURANCE.