റ്റ

A Malayalam ligature from 2 റ (ṟa) but pronounced as /t:a/.

In older forms (still used rarely) 2 adjacent റ's (ററ) was used to represent /t:a/ and it could also be read as /rara/.

In the 1800s a separate letter ഺ (ṯa) was made by A.R. Rajarajavarma to represent the phoneme /ta/ but it didnt became popular.