select-object-with-max-value.ps1

# all files
$a = Get-Item *.txt

# prefix of latest file
$b = $a |
  sort -Property LastWriteTime -Descending |
  select -First 1 @{n='dts';e={$_.name.split('_')[0]}}).dts

# files with that prefix
Get-Item "$b*.txt"


# one-liner that I actually did
(Get-Item ("{0}*.txt" -f $((Get-Item *.txt) |
  sort -Property LastWriteTime -Descending |
  select -First 1 @{n='dts';e={$_.name.split('_')[0]}}).dts))