The　phase　transition　of　Nd2In　and　Pr2In　has　been　studied　and　found　to　be　between　the　first-order　and　second-order　nature.　Hardly　any　hysteresis　nor　obvious　cell　volume　changes　are　presented.　Concurrently　the　field-triggered　metamagnetism　is　demonstrated　with　lambda-like　peak　on　specific　heat　curve.　For　the　field　change　of　7　T,　giant　magnetic　entropy　changes　of　13.2　J　kg−1　K−1　and　19.5　J　kg−1　K−1　and　adiabatic　temperature　changes　of　6.5　K　and　7.4　K　have　been　achieved　in　Nd2In　and　Pr2In　alloys　respectively,　which　is　partially　contributed　by　strong　magnetoelastic　coupling　represented　by　high　saturation　magnetostriction　of　∼450　ppm.　Such　unique　feature　is　proposed　to　be　originated　from　the　delocalized　5d　electrons,　as　evidenced　by　the　negative　magnetoresistance　caused　by　the　phase　transition.　©　2021