Powershell duplicate file search

Get-DuplicateFiles.ps1

function Get-DuplicateFiles
{
    param
    (
        [Parameter(Mandatory=$true)]
        [string] $Directory
    )

    $Duplicates = @{}

    ls -Recurse -File $Directory |
        select -ExpandProperty FullName |
        % { Get-FileHash $_ -Algorithm SHA512 } |
        % { $key = $_.Hash;
            if ($Duplicates[$key] -eq $null) { $Duplicates[$key] = @() }
            $Duplicates[$key] += $_.Path
        }


    $uniqueHashes = $Duplicates.Keys | ? { $Duplicates[$_].Count -lt 2 }

    $uniqueHashes | % { $Duplicates.Remove($_) }

    $Duplicates
}