This planet was only mentioned in dialogue.
"AM-leth" was the pronunciation for this planet's name from the script pronunciation guide. 
According to Star Trek: Star Charts (p. 46) and Stellar Cartography: The Starfleet Reference Library ("Stellar Cartography", pp. 18-19; "Federation Historical Highlights, 2161-2385"), the Amleth system was located in the Alpha Quadrant. According to a map of the Cardassian Union – prepared by an anonymous astrography clerk, from the Cardassian Central Archives, in 2364 – Amleth was identified as a Cardassian system.